The following fans may be defined either in the air loop or
as a zone equipment component: Fan:ConstantVolume,
Fan:OnOff,
Fan:VariableVolume,
Fan:ZoneExhaust,
and FanPerformance:NightVentilation.
The data that are common to these fan types include an
identifying name, an availability schedule name, a total
efficiency rating, a rated pressure rise, and inlet and outlet
air node names. In the case of a variable volume fan,
additional input includes parameters for modeling fan
performance over a range of fan speeds. See the engineering
documentation for the variable speed fan for a further
description of what these coefficients represent.
Commonly-used values for different variable volume systems are
shown in the following table.
Fan Coefficient Values
| Type of Fan |
Fan Coeff. 1 |
Fan Coeff. 2 |
Fan Coeff. 3 |
Fan Coeff. 4 |
Fan Coeff. 5 |
| Inlet Vane Dampers |
0.35071223 |
0.30850535 |
-0.54137364 |
0.87198823 |
0.000 |
| Discharge Dampers |
0.37073425 |
0.97250253 |
-0.34240761 |
0.000 |
0.000 |
| Var. Speed Motor |
0.0015302446 |
0.0052080574 |
1.1086242 |
-0.11635563 |
0.000 |
Fan:ConstantVolume[LINK]
This object models a constant air volume fan that is
intended to operate continuously based on a time schedule.
This fan will not cycle on and off based on cooling/heating
load or other control signals (Ref: Fan:OnOff).
A unique user-assigned name for an instance of a Fan:ConstantVolume.
Any reference to this fan by another object will use this
name.
Field:
Availability Schedule Name[LINK]
The name of the schedule (ref: Schedule) that denotes
whether the fan can run during a given time period. A schedule
value of 0 indicates that the fan is off for that time period.
A schedule value greater than 0 indicates that the fan can
operate during the time period. If this field is blank, the
schedule has values of 1 for all time periods. Applicable
availability managers (ref. AvailabilityManagerAssignmentList)
may override this schedule by forcing the fan to be on or
off.
Field: Fan Total
Efficiency[LINK]
This value is the overall efficiency of the fan, i.e., the
ratio of the power delivered to the fluid to the electrical
input power. It is the product of the motor efficiency and the
impeller efficiency. The motor efficiency is the power
delivered to the shaft divided by the electrical power input
to the motor. The impeller efficiency is power delivered to
the fluid (air) divided by the shaft power. The power
delivered to the fluid is the mass flow rate of the air
multiplied by the pressure rise divided by the air density.
This input value must be between 0 and 1.The default is
0.7.
Field: Pressure Rise[LINK]
The pressure rise in Pascals at full flow and standard (sea
level) conditions (20 °C and 101325 Pa).
Field: Maximum Flow
Rate[LINK]
The full load air volumetric flow rate (m\(^{3}\)/sec) at standard
temperature and pressure (dry air at 20 °C drybulb). The
program does use local barometric pressure to account for
altitude using equation for “standard atmospheric” pressure on
p 6.1 of the ASHRAE 1997 HOF (SI edition) to initialize the
air systems being simulated.
p = 101325*(1-2.25577E-05*Z)**5.2559
where p = pressure in Pa and Z = altitude in m
Field: Motor Efficiency[LINK]
The shaft power divided by the electrical power consumed.
Must be between 0 and 1. The default is 0.9.
Field: Motor In
Airstream Fraction[LINK]
The fraction of the motor heat that is added to the air
stream. A value of 0 means that the motor is completely
outside the air stream. A value of 1 means that all of the
motor heat loss will go into the air stream and act to cause a
temperature rise. Must be between 0 and 1. The default is
1.0.
Field: Air Inlet Node
Name[LINK]
The name of the HVAC system node which supplies the inlet
air conditions to the fan.
Field: Air Outlet Node
Name[LINK]
The name of the HVAC system node to which the fan sends its
outlet air.
Field: End-Use
Subcategory[LINK]
Allows you to specify a user-defined end-use subcategory,
e.g., “Central System”, etc. A new meter for reporting is
created for each unique subcategory (ref: Output:Meter
objects). Subcategories are also reported in the ABUPS table.
If this field is omitted or blank, the fan will be assigned to
the “General” end-use subcategory.
HVAC,Average,Fan Electric Power[W]
HVAC,Average,Fan Rise in Air Temperature
[deltaC]
HVAC,Sum,Fan Electric Energy [J]
Fan Electric Power [W][LINK]
This output field contains the average electricity
consumption rate for the fan in Watts for the timestep being
reported.
Fan Rise in Air
Temperature [deltaC][LINK]
This output field contains the average rise in air
temperature across the fan (outlet air temperature minus inlet
air temperature) in degrees Celsius for the timestep being
reported.
Fan Electric Energy [J][LINK]
This output field contains the electricity consumption of
the fan in Joules for the timestep being reported. This output
is also added to a meter with Resource Type = Electricity, End
Use Key = Fans, Group Key = System (ref. Output:Meter
objects).
This object models a constant air volume fan that is
intended to cycle on and off in tandem with a cooling or
heating system (i.e., AUTO fan control mode). The fan can also
operate continuously like Fan:ConstantVolume.
If modeling continuous operation and this object is used as
part of a system that utilizes Coil:Heating:Gas,
Coil:Cooling:DX:SingleSpeed
or Coil:Heating:DX:SingleSpeed,
the user should confirm proper air flow rates (coil and fan
max flows are equal) and that the coil part-load fraction
correlation(s) are appropriate (e.g., part-load fraction is
less than or equal to 1 for all values of coil part-load
ratio). If modeling multi-speed fan operation, this object
must be used as part of a compound object that allows multiple
fan speeds (e.g., AirLoopHVAC:Unitary:Furnace:HeatCool,
ZoneHVAC:PackagedTerminalAirConditioner,
etc.). In this case, the ratio of the compound object air flow
rate to the fan s maximum air flow rate is used to determine
the power at alternate fan speeds. The optional input for Fan
Power Ratio Function of Speed Ratio Curve Name must be entered
to model multi-speed fan operation. An optional fan total
efficiency ratio curve is also available to model efficiency
differences at alternate fan speeds.
A unique user-assigned name for an instance of a Fan:OnOff.
Any reference to this fan by another object will use this
name.
Field:
Availability Schedule Name[LINK]
The name of the schedule (ref: Schedule) that denotes
whether the fan can run during a given time period. A schedule
value of 0 indicates that the fan is off for that time period.
A schedule value greater than 0 indicates that the fan can
operate during the time period. If this field is blank, the
schedule has values of 1 for all time periods. Applicable
availability managers (ref. AvailabilityManagerAssignmentList)
may override this schedule by forcing the fan to be on or
off.
Field: Fan Total
Efficiency[LINK]
This value is the overall efficiency of the fan, i.e., the
ratio of the power delivered to the fluid to the electrical
input power. It is the product of the motor efficiency and the
impeller efficiency. The motor efficiency is the power
delivered to the shaft divided by the electrical power input
to the motor. The impeller efficiency is power delivered to
the fluid (air) divided by the shaft power. The power
delivered to the fluid is the mass flow rate of the air
multiplied by the pressure rise divided by the air density.
This input value must be between 0 and 1.The default is
0.6.
Field: Pressure Rise[LINK]
The pressure rise in Pascals at full flow and standard (sea
level) conditions (20 °C and 101325 Pa).
Field: Maximum Flow Rate[LINK]
The full load air volumetric flow rate (m\(^{3}\)/sec) at standard
temperature and pressure (dry air at 20 °C drybulb). The
program does use local barometric pressure to account for
altitude using equation for “standard atmospheric” pressure on
p 6.1 of the ASHRAE 1997 HOF (SI edition) to initialize the
air systems being simulated.
p = 101325*(1-2.25577E-05*Z)**5.2559
where p = pressure in Pa and Z = altitude in m
Field: Motor Efficiency[LINK]
The shaft power divided by the electrical power consumed.
Must be between 0 and 1. The default is 0.8.
Field: Motor In
Airstream Fraction[LINK]
The fraction of the motor heat that is added to the air
stream. A value of 0 means that the motor is completely
outside the air stream. A value of 1 means that all of the
motor heat loss will go into the air stream and act to cause a
temperature rise. Must be between 0 and 1. The default is
1.0.
Field: Air Inlet Node
Name[LINK]
The name of the HVAC system node which supplies the inlet
air conditions to the fan.
Field: Air Outlet
Node Name[LINK]
The name of the HVAC system node to which the fan sends its
outlet air.
Field:
Fan Power Ratio Function of Speed Ratio Curve Name[LINK]
Enter the name of an exponent performance curve. This
optional alpha field must be used to simulate multi-speed fan
motors. This curve represents the ratio of actual fan power to
rated fan power when a change in fan speed occurs. Leave this
field blank when simulating constant-speed fan motors.
Field:
Fan Efficiency Ratio Function of Speed Ratio Curve Name[LINK]
Enter the name of a quadratic or cubic performance curve.
This optional alpha field is used to simulate multi-speed fan
motors. This curve represents the ratio of actual fan total
efficiency to rated fan total efficiency when a change in fan
speed occurs. Leave this field blank when simulating
constant-speed fan motors.
Field: End-Use
Subcategory[LINK]
Allows you to specify a user-defined end-use subcategory,
e.g., “Main Fans”, etc. A new meter for reporting is created
for each unique subcategory (ref: Output:Meter
objects). Subcategories are also reported in the ABUPS table.
If this field is omitted or blank, the fan will be assigned to
the “General” end-use subcategory.
Following is an example input for an OnOff Fan.
Fan:OnOff,
Supply Fan 1, ! Fan Name
FanAndCoilAvailSched, ! Fan Schedule
0.7, ! Fan Total Efficiency
600.0, ! Delta Pressure [N/M^2]
1.3, ! Max Flow Rate [m^3/Sec]
0.9, ! Motor Efficiency
1.0, ! Motor in Airstream Fraction (1.0 means motor in air stream)
Air Loop Inlet Node, Cooling Coil Air Inlet Node; !Inlet Node, Outlet Node
HVAC,Average,Fan Electric Power[W]
HVAC,Average,Fan Rise in Air Temperature [deltaC]
HVAC,Sum,Fan Electric Energy [J]
HVAC,Average,Fan Runtime Fraction []
Fan Electric Power [W][LINK]
This output field contains the average electricity
consumption rate for the fan in Watts for the timestep being
reported.
Fan Rise in Air
Temperature [deltaC][LINK]
This output field contains the average rise in air
temperature across the fan (outlet air temperature minus inlet
air temperature) in degrees Celsius for the timestep being
reported.
Fan Electric Energy [J][LINK]
This output field contains the electricity consumption of
the fan in Joules for the timestep being reported. This output
is also added to a meter with Resource Type = Electricity, End
Use Key = Fans, Group Key = System (ref. Output:Meter
objects).
Fan Runtime Fraction [][LINK]
This output field contains the fraction of time that this
fan operated for the timestep being reported.
Fan:VariableVolume[LINK]
A unique user-assigned name for an instance of a Fan:VariableVolume.
Any reference to this fan by another object will use this
name.
Field:
Availability Schedule Name[LINK]
The name of the schedule (ref: Schedule) that denotes
whether the fan can run during a given time period. A schedule
value of 0 indicates that the fan is off for that time period.
A schedule value greater than 0 indicates that the fan can
operate during the time period. If this field is blank, the
schedule has values of 1 for all time periods. Applicable
availability managers (ref. AvailabilityManagerAssignmentList)
may override this schedule by forcing the fan to be on or
off.
Field: Fan Total
Efficiency[LINK]
This value is the overall efficiency of the fan, i.e., the
ratio of the power delivered to the fluid to the electrical
input power. It is the product of the motor efficiency and the
impeller efficiency. The motor efficiency is the power
delivered to the shaft divided by the electrical power input
to the motor. The impeller efficiency is power delivered to
the fluid (air) divided by the shaft power. The power
delivered to the fluid is the mass flow rate of the air
multiplied by the pressure rise divided by the air density.
This input value must be between 0 and 1. The default is
0.7.
Field: Pressure Rise[LINK]
The pressure rise in Pascals at full flow and standard (sea
level) conditions (20 °C and 101325 Pa).
Field: Maximum Flow
Rate[LINK]
The full load air volumetric flow rate (m\(^{3}\)/sec) at standard
temperature and pressure (dry air at 20 °C drybulb). The
program does use local barometric pressure to account for
altitude using equation for “standard atmospheric” pressure on
p 6.1 of the ASHRAE 1997 HOF (SI edition) to initialize the
air systems being simulated.
p = 101325*(1-2.25577E-05*Z)**5.2559
where p = pressure in Pa and Z = altitude in m
This field is a key/choice field that tells which of the
next two fields is filled and is descriptive of how the
minimum flow rate is specified for calculating the fan power.
The key/choices are:
With this choice, the fan power will be calculated using
the value specified in the Fan Power Minimum Flow Fraction
field. (The Fan Power Minimum Flow Fraction field should be
filled.)
With this choice, the fan power will be calculated using
the value specified in the Fan Power Minimum Air Flow Rate
field. (The Fan Power Minimum Air Flow Rate field should be
filled.)
The default is Fraction.
Field: Fan
Power Minimum Flow Fraction[LINK]
The minimum air volumetric flow rate for fan power,
specified as a fraction of maximum system air flow rate. Must
be between 0 and 1. Note that this field is only used to
calculate the fan power. This field does not enforce the
system air flow rate during simulation. The default is
0.25.
Field: Fan
Power Minimum Air Flow Rate[LINK]
The minimum air volumetric flow rate for fan power,
specified as a constant minimum air flow rate (m3/sec). Note
that this field is only used to calculate the fan power. This
field does not enforce the system air flow rate during
simulation.
Field: Motor Efficiency[LINK]
The shaft power divided by the electrical power consumed.
Must be between 0 and 1. The default is 0.9.
Field: Motor In
Airstream Fraction[LINK]
The fraction of the motor heat that is added to the air
stream. A value of 0 means that the motor is completely
outside the air stream. A value of 1 means that all of the
motor heat loss will go into the air stream and act to cause a
temperature rise. Must be between 0 and 1. The default is
1.0.
Field: Fan Power
Coefficient 1[LINK]
The constant coefficient (C\(_{1}\)) in a fourth order
polynomial curve giving the fraction of full load power (PLF)
as a function of flow fraction (FF). Flow fraction is the air
mass flow rate divided by the maximum air mass flow rate. The
curve is:
PLF = C\(_{1}\) + C\(_{2}\)\(^{.}\) FF + C\(_{3}\)\(^{.}\) FF\(^{2\\ +}\) C\(_{4}\)\(^{.}\) FF\(^{3}\) + C\(_{5}\)\(^{.}\) FF\(^{4}\)
Field: Fan Power
Coefficient 2[LINK]
The linear coefficient (C\(_{2}\)) in a fourth order
polynomial curve giving the fraction of full load power (PLF)
as a function of flow fraction (FF). Flow fraction is the air
mass flow rate divided by the maximum air mass flow rate. The
curve is:
PLF = C\(_{1}\) + C\(_{2}\)\(^{.}\) FF + C\(_{3}\)\(^{.}\) FF\(^{2\\ +}\) C\(_{4}\)\(^{.}\) FF\(^{3}\) + C\(_{5}\)\(^{.}\) FF\(^{4}\)
Field: Fan Power
Coefficient 3[LINK]
The quadratic coefficient (C\(_{3}\)) in a fourth order
polynomial curve giving the fraction of full load power (PLF)
as a function of flow fraction (FF). Flow fraction is the air
mass flow rate divided by the maximum air mass flow rate. The
curve is:
PLF = C\(_{1}\) + C\(_{2}\)\(^{.}\) FF + C\(_{3}\)\(^{.}\) FF\(^{2\\ +}\) C\(_{4}\)\(^{.}\) FF\(^{3}\) + C\(_{5}\)\(^{.}\) FF\(^{4}\)
Field: Fan Power
Coefficient 4[LINK]
The cubic coefficient (C\(_{1}\)) in a fourth order
polynomial curve giving the fraction of full load power (PLF)
as a function of flow fraction (FF). Flow fraction is the air
mass flow rate divided by the maximum air mass flow rate. The
curve is:
PLF = C$_{1}$ + C$_{2}$$^{.}$ FF + C$_{3}$$^{.}$ FF$^{2\\ +}$ C$_{4}$$^{.}$ FF$^{3}$ + C$_{5}$$^{.}$ FF$^{4}$
Field: Fan Power
Coefficient 5[LINK]
The coefficient C\(_{5}\)
in a fourth order polynomial curve giving the fraction of full
load power (PLF) as a function of flow fraction (FF). Flow
fraction is the air mass flow rate divided by the maximum air
mass flow rate. The curve is:
PLF = C$_{1}$ + C$_{2}$$^{.}$ FF + C$_{3}$$^{.}$ FF$^{2\\ +}$ C$_{4}$$^{.}$ FF$^{3}$ + C$_{5}$$^{.}$ FF$^{4}$
Field: Air Inlet Node
Name[LINK]
The name of the HVAC system node which supplies the inlet
air conditions to the fan.
Field: Air Outlet
Node Name[LINK]
The name of the HVAC system node to which the fan sends its
outlet air.
Field: End-Use
Subcategory[LINK]
Allows you to specify a user-defined end-use subcategory,
e.g., “Central System”, etc. A new meter for reporting is
created for each unique subcategory (ref: Output:Meter
objects). Subcategories are also reported in the ABUPS table.
If this field is omitted or blank, the fan will be assigned to
the “General” end-use subcategory.
HVAC,Average,Fan Electric Power[W]
HVAC,Average,Fan Rise in Air Temperature
[deltaC]
HVAC,Sum,Fan Electric Energy [J]
Fan Electric Power [W][LINK]
This output field contains the average electricity
consumption rate for the fan in Watts for the timestep being
reported.
Fan Rise in Air
Temperature [deltaC][LINK]
This output field contains the average rise in air
temperature across the fan (outlet air temperature minus inlet
air temperature) in degrees Celsius for the timestep being
reported.
Fan Electric Energy [J][LINK]
This output field contains the electricity consumption of
the fan in Joules for the timestep being reported. This output
is also added to a meter with Resource Type = Electricity, End
Use Key = Fans, Group Key = System (ref. Output:Meter
objects).
Fan:ZoneExhaust[LINK]
This fan object differs from the other fans in that it
stands on its own in a zone rather than serving as one part of
an HVAC air system. This object appears directly in a ZoneHVAC:EquipmentList
object and all the controls are contained within the fan
object. The zone exhaust fan model provides a way to include
the electrical power used by the fan. It can also impact air
flows in central air handlers by decreasing the flow of return
air and sometimes increasing the outdoor air flow rate.
There are several control options available for the exhaust
fan including: an on/off availability schedule, interaction
with system availability managers, minimum zone air
temperature control limits and a variable flow fraction
schedule.
The way in which the exhaust fan impacts central air system
can be controlled by declaring what portion of the flow has
been balanced by simple airflow from infiltration,
ventilation, or mixing. However it is important to note that
presence of an exhaust fan does not by itself drive any simple
airflow such as infiltration, ventilation, or zone mixing.
There is no comprehensive automatic mass balancing between air
system flows, exhaust flows, and the separate simple airflows.
For balancing, the simple airflows need to have their own
input objects that need to be coordinated with the exhaust
fan.
A unique user-assigned name for an instance of a Fan:ZoneExhaust.
Any reference to this fan by another object will use this
name.
Field:
Availability Schedule Name[LINK]
The name of the schedule (ref: Schedule) that denotes
whether the fan can run during a given time period. A schedule
value of 0 indicates that the fan is off for that time period.
A schedule value greater than 0 indicates that the fan can
operate during the time period. If this field is blank, the
schedule has values of 1 for all time periods. Applicable
availability managers (ref. AvailabilityManagerAssignmentList)
may override this schedule by forcing the fan to be on or
off.
Field: Fan Total
Efficiency[LINK]
This value is the overall efficiency of the fan, i.e., the
ratio of the power delivered to the fluid to the electrical
input power. It is the product of the motor efficiency and the
impeller efficiency. The motor efficiency is the power
delivered to the shaft divided by the electrical power input
to the motor. The impeller efficiency is power delivered to
the fluid (air) divided by the shaft power. The power
delivered to the fluid is the mass flow rate of the air
multiplied by the pressure rise divided by the air density.
This input value must be between 0 and 1. The default is
0.6.
Field: Pressure Rise[LINK]
The pressure rise in Pascals at full flow and standard (sea
level) conditions (20 °C and 101325 Pa).
Field: Maximum Flow
Rate[LINK]
The full load air volumetric flow rate (m\(^{3}\)/sec) at standard
temperature and pressure (dry air at 20 °C drybulb). The
program does use local barometric pressure to account for
altitude using equation for “standard atmospheric” pressure on
p 6.1 of the ASHRAE 1997 HOF (SI edition) to initialize the
air systems being simulated.
p = 101325*(1-2.25577E-05*Z)**5.2559
where p = pressure in Pa and Z = altitude in m
Field: Air Inlet Node
Name[LINK]
The name of the HVAC system node which supplies the inlet
air conditions to the fan. This node should be listed as a
zone exhaust node in an associated ZoneHVAC:EquipmentConnections
object.
Field: Air Outlet
Node Name[LINK]
The name of the HVAC system node to which the fan sends its
outlet air.
Field: End-Use
Subcategory[LINK]
Allows you to specify a user-defined end-use subcategory,
e.g., “Kitchen Exhaust”, “Fume Hoods”, etc. A new meter for
reporting is created for each unique subcategory (ref: Output:Meter
objects). Subcategories are also reported in the ABUPS table.
If this field is omitted or blank, the fan will be assigned to
the “General” end-use subcategory.
Field: Flow
Fraction Schedule Name[LINK]
This field is optional. If it is not used then the fan
operates at the maximum flow rate. If a schedule is input
here, then it should contain fractional values between 0.0 and
1.0, inclusive. The flow rate that the fan operates will be
this fraction times the maximum flow rate. This allows a
variable speed exhaust fan to be modeled according to a
schedule.
Field:
System Availability Manager Coupling Mode[LINK]
This field is optional. If if is not used then the exhaust
fan is assumed to be integrated with the central air handler s
system availability manager. This field can be used to control
if the exhaust fan should operate independently or not. For
example, when a night cycle availability manager turns on the
central air system for freeze protection, this field can be
used to control if the zone exhaust fans should also run at
the same time or not. The key choice Coupled indicates that
the exhaust fan should be integrated with the system
availability manager so that the fan runs when the air system
is forced to run. The key choice Decoupled indicates that the
exhaust fan should operate on its own and ignore the system
availability manager s requests so that the exhaust fan can
remain off when the air system runs. The default is
Coupled.
Field:
Minimum Zone Temperature Limit Schedule Name[LINK]
This field is optional. If it is not used then there will
be no temperature-related control over the operation of the
exhaust fan. If the field is used, then enter the name of a
schedule with values for zone temperature values ( °C). The
fan s control will be based on a comparison between the
current zone air temperature and the schedule values. If the
zone is warmer than the scheduled limit, then the fan will
operate. When balancing with simple ventilation, this feature
can be used to coordinate exhaust fan operation with
ZoneVentilation:* controls for minimum indoor temperature.
Field:
Balanced Exhaust Fraction Schedule Name[LINK]
This field is optional. If it is not used, then all the
exhaust air flow is assumed to be unbalanced by any simple
airflows, such as infiltration, ventilation, or zone mixing.
Unbalanced exhaust is then modeled as being provided by the
outdoor air system in the central air system. The modeling of
unbalanced will reduce the flow rates at the zone s return air
node by the flow rate that is being exhausted and will insure
that the outdoor air flow rate is sufficient to serve the
exhaust. If this field is used, then enter the name of a
schedule with fractional values between 0.0 and 1.0,
inclusive. This fraction is applied to the exhaust fan flow
rate and the model tracks the portion of the exhaust that is
balanced. Balanced exhaust is then modeled as being provided
by simple airflows and does not impact the central air system
return air or outdoor air flow rates. For example, if a
kitchen zone with an exhaust fan is designed to draw half of
its make up air from a neighboring dining room and the other
half from the outdoor air system, then a schedule value of 0.5
could be used here.
HVAC,Average,Fan Electric Power [W]
HVAC,Average,Fan Rise in Air
Temperature[deltaC]
HVAC,Sum,Fan Electric Energy [J]
HVAC,Average,Fan Unbalanced Air Mass Flow Rate
[kg/s]
HVAC,Average,Fan Balanced Air Mass Flow Rate
[kg/s]
Fan Electric Power [W][LINK]
This output field contains the average electricity
consumption rate for the fan in Watts for the timestep being
reported.
Fan Rise in Air
Temperature [deltaC][LINK]
This output field contains the average rise in air
temperature across the fan (outlet air temperature minus inlet
air temperature) in degrees Celsius for the timestep being
reported.
Fan Electric Energy [J][LINK]
This output field contains the electricity consumption of
the fan in Joules for the timestep being reported. This output
is also added to an output meter with Resource Type =
Electricity, End Use Key = Fans, Group Key = System (ref. Output:Meter
objects).
Fan Unbalanced
Air Mass Flow Rate [kg/s][LINK]
Fan Balanced Air
Mass Flow Rate [kg/s][LINK]
These two output variables are available when the exhaust
fan uses the input field called Balanced Exhaust Fraction
Schedule Name. The balanced air flow is the result of the
current flow rate times the balance fraction. The unbalanced
air flow is the difference between the current flow rate and
the balanced flow rate. These outputs are the resulting flow
rates in kg/s.
Examples of Fan:ConstantVolume,
Fan:VariableVolume,
Fan:ZoneExhaust,
and , Fan:OnOff,
fans in an IDF are:
Fan:ConstantVolume,
Supply Fan 1, !- Name
FanAndCoilAvailSched, !- Availability Schedule Name
0.7, !- Fan Total Efficiency
600.0, !- Pressure Rise {Pa}
1.3, !- Maximum Flow Rate {m3/sec}
0.9, !- Motor Efficiency
1.0, !- Motor in Airstream Fraction
Air Loop Inlet Node, Cooling Coil Air Inlet Node; !- Air Inlet Node Name, Air Outlet Node Name
Fan:VariableVolume,
Var Vol Supply Fan 1, !- Name
FanAndCoilAvailSched, !-Availability Schedule Name
0.7, !- Fan Total Efficiency
600.0, !- Pressure Rise {Pa}
1.3, !- Maximum Flow Rate {m3/s}
0.20, !- Minimum Flow Rate {m3/s}
0.9, !- Motor Efficiency
1.0, !- Motor in Airstream Fraction
0.35071223, !- Fan Coefficient 1
0.30850535, !- Fan Coefficient 2
-0.54137364, !- Fan Coefficient 3
0.87198823, !- Fan Coefficient 4
0.000, !- Fan Coefficient 5
Air Loop Inlet Node, Cooling Coil Air Inlet Node; !- Air Inlet Node Name,Air Outlet Node Name
Fan:ZoneExhaust,
Zone 2 Exhaust Fan, !-Name
FanAndCoilAvailSched, !-Availability Schedule Name
0.6, !-Fan Total Efficiency
125, !-Pressure Rise {Pa}
0.1, !-Maximum Flow Rate {m3/s}
Zone 2 Exhaust Node, !-Air Inlet Node Name
Zone 2 Exhaust Fan Outlet Node, !-Air Outlet Node Name
Kitchen Exhaust; !- End-Use Subcategory
Fan:OnOff,
AHU 1 Supply Fan, !- Name
FanAvailSched, !- Availability Schedule Name
0.7, !- Fan Total Efficiency
600.0, !- Pressure Rise {Pa}
2.0, !- Maximum Flow Rate {m3/s}
0.9, !- Motor Efficiency
1.0, !- Motor in Airstream Fraction
AHU 1 Air Loop Inlet, !- Air Inlet Node Name
AHU 1 Supply Fan Outlet; !- Air Outlet Node Name
This object is used for specifying an alternate set of
performance parameters for a fan. These alternate parameters
are used when a system manager (such as AvailabilityManager:NightVentilation)
sets a specified flow rate for a central forced air system. At
this time, it can be used with Fan:ConstantVolume,
Fan:VariableVolume,
Fan:ZoneExhaust,
and , Fan:OnOff
fans, but not with Fan:ComponentModel
fans. The fan model checks whether a fixed flow rate has been
set; if it has the fan model will use these alternate
performance parameters. Note that it is assumed that the fan
will run at a fixed speed in the alternate mode. The inputs
needed by this object are the fan name, fan total efficiency,
pressure rise, flow rate, motor efficiency, and motor in
airstream fraction.
Field: Fan Name[LINK]
This is the name of a fan defined elsewhere in the input
file. The night vent performance parameters will be applied to
the named fan when a system manager has set the air system
flow rate.
Field: Fan Total
Efficiency[LINK]
This value is the overall efficiency of the fan, i.e., the
ratio of the power delivered to the fluid to the electrical
input power. It is the product of the motor efficiency and the
impeller efficiency. The motor efficiency is the power
delivered to the shaft divided by the electrical power input
to the motor. The impeller efficiency is power delivered to
the fluid (air) divided by the shaft power. The power
delivered to the fluid is the mass flow rate of the air
multiplied by the pressure rise divided by the air density.
This input value must be between 0 and 1. This is a required
field with no default.
Field: Pressure Rise[LINK]
The pressure rise in Pascals at full flow and standard (sea
level) conditions (20 °C and 101325 Pa).
Field: Maximum Flow
Rate[LINK]
The design volumetric flow rate of the fan (m\(^{3}\)/sec) at standard
conditions. This input is not currently used by the night
ventilation manager. The flow rate during night ventilation is
specified using the SystemAvailabilityManager:NightVentilation
“Night Venting Flow Fraction” field. This fraction is
multiplied times the fan object’s design flow rate.
Field: Motor Efficiency[LINK]
The shaft power divided by the electrical power consumed.
Must be between 0 and 1. This is a required field with no
default.
Field: Motor in
Airstream Fraction[LINK]
The fraction of the motor heat that is added to the air
stream. A value of 0 means that the motor is completely
outside the air stream. A value of 1 means that all of the
motor heat loss will go into the air stream and act to cause a
temperature rise. Must be between 0 and 1. The default is
1.0.
An example of use in an IDF:
Fan:VariableVolume,
Supply Fan 1, !- Name
FanAvailSched, !- Availability Schedule Name
0.7, !- Fan Efficiency
600.0, !- Pressure Rise {Pa}
autosize, !- Maximum Flow Rate {m3/s}
autosize, !- Minimum Flow Rate {m3/s}
0.9, !- Motor Efficiency
1.0, !- Motor In Airstream Fraction
0.35071223, !- Fan Coefficient 1
0.30850535, !- Fan Coefficient 2
-0.54137364, !- Fan Coefficient 3
0.87198823, !- Fan Coefficient 4
0.000, !- Fan Coefficient 5
Main Heating Coil 1 Outlet Node, !- Air Inlet Node Name
VAV Sys 1 Outlet Node; !- Air Outlet Node Name
FanPerformance:NightVentilation,
Supply Fan 1, !- Fan Name
0.7, !- Fan Total Efficiency
67.0, !- Pressure Rise {Pa}
autosize, !- Maximum Flow Rate {m3/s}
0.9, !- Motor Efficiency
1.0; !- Motor in Airstream Fraction
Fan:ComponentModel[LINK]
The Fan:ComponentModel
fan is a more detailed fan type that can be defined in the air
loop for central constant-air-volume (CAV) and
variable-air-volume (VAV) systems. It includes inputs that
describe the air-distribution system as well as the fan, its
drive belt (if used), its motor, and its
variable-frequency-drive (if used). See the engineering
documentation for further descriptions about the inputs for
this fan type.
The required unique user-assigned alpha name for an
instance of a Fan:ComponentModel.
Any reference to this fan by another object will use this
name.
Field: Air Inlet Node
Name[LINK]
The required alpha name of the HVAC system node which
supplies the inlet air conditions to the fan.
Field: Air Outlet
Node Name[LINK]
The required alpha name of the HVAC system node to which
the fan sends its outlet air.
Field:
Availability Schedule Name[LINK]
The required alpha name of the schedule (ref: Schedule)
that denotes whether the fan can run during a given time
period. A schedule value of 0 indicates that the fan is off
for that time period. A schedule value greater than 0
indicates that the fan can operate during the time period. If
this field is blank, the schedule has values of 1 for all time
periods. Applicable availability managers (ref.
AvailabilityManagerAssignmentList) may override this schedule
by forcing the fan to be on or off.
Field: Maximum Flow
Rate[LINK]
The full-load volumetric airflow (m\(^{3}\)/sec) through the fan at
standard temperature and pressure (dry air at 20 °C dry-bulb).
To initialize the air systems being simulated, the program
uses local barometric pressure adjusted for altitude, based on
the equation for “standard atmospheric” pressure on p.6.1 of
the 1997 ASHRAE Handbook of Fundamentals (SI edition):
p = 101325 * (1 - 2.25577E-05 * Z)**5.2559
where p = pressure in Pa and Z = altitude in m. Can be
autosized.
Specified or autosized maximum airflow rate (including
effects of scaling by Field: Fan Sizing Factor) along with
corresponding fan static pressure rise and fan shaft power are
reported in the .eio file as, respectively, Design Fan Airflow
[m3/s], Design Fan Static Pressure Rise [Pa], and Design Fan
Shaft Power [W].
Field: Minimum Flow Rate[LINK]
The minimum volumetric airflow (m\(^{3}\)/sec) through the fan at
standard temperature and pressure (see Maximum Flow Rate field
above for condition details). Can be autosized.
Field: Fan Sizing Factor[LINK]
The numeric dimensionless factor (F\(_{fan}\)) used to multiply
the specified or autosized full-load volumetric airflow (see
Maximum Flow Rate field above for details) for fan sizing. If
specified, minimum value is 1.0. Default is 1.0 if field is
blank.
Field: Fan Wheel
Diameter[LINK]
The required numeric outer diameter of the fan wheel
(D\(_{fan}\), m).
This value is determined from manufacturer s data. In general,
larger diameter fans have higher maximum efficiency than
smaller diameter fans of the same type (Ref: AMCA Standard
205-10: Energy Efficiency Classification for Fans). Must be
greater than zero.
Field: Fan Outlet Area[LINK]
The required numeric outlet area of the fan (A\(_{fan,out}\), m\(^{2}\)). This value is determined
from manufacturer s data. It is used to convert fan total
pressure rise to fan static pressure rise. Fan static pressure
rise is the fan total pressure rise minus the fan outlet
velocity pressure; it is not the difference between fan outlet
and inlet static pressures (Ref: ANSI/AMCA Standard 210-07,
ANSI/ASHRAE Standard 51-07: Laboratory Methods of Testing Fans
for Certified Aerodynamic Performance Rating). Must be greater
than zero.
Field: Maximum
Fan Static Efficiency[LINK]
The required numeric maximum ratio (\(\eta_{fan,max}\) ) between the
power delivered to the air (H\(_{air}\), W) and the fan
shaft input power (H\(_{fan}\), W). For this
parameter, H\(_{air}\) is the volumetric
airflow through the fan multiplied by the fan static pressure
rise. Maximum fan static efficiency is determined from
analyses of manufacturers data using:
\[{\eta_{fan,\max }} = \max
\left[ {\frac{{\left( {\Delta {P_{fan}} * {Q_{fan}}}
\right)}}{{{H_{fan}}}}} \right]\]
where P\(_{fan}\)
is fan static pressure rise (Pa) and Q\(_{fan}\) is airflow through
the fan (m\(^{3}\)/sec).
Typically, do not select curves on fan performance maps of
pressure rise versus flow correspond to or are near maximum
efficiency. Must be greater than zero and less than or equal
to 1.0.
Calculated fan static efficiency at design flow condition
(including part-load effects of oversized fan) is reported in
the .eio file as Design Fan Efficiency [-].
Field:
Euler Number at Maximum Fan Static Efficiency[LINK]
The required numeric Euler number (Eu\(_{max}\)), which is also
called the throttling or pressure coefficient, and is the
ratio of pressure forces to inertial forces. The Euler number
is determined from analyses of manufacturer s data using:
\[Eu = \frac{{\left( {\Delta
{P_{fan}} * D_{fan}^4} \right)}}{{\left( {\rho * Q_{fan}^2}
\right)}}\]
where P\(_{fan}\)
is fan static pressure rise (Pa; see Fan Pressure Rise
Curve Name field), D\(_{fan}\) is wheel diameter
(m), ρ is the manufacturer s reference air density
(kg/m\(^{3}\)), and
Q\(_{fan}\) is
airflow through the fan (m\(^{3}\)/sec). Eu\(_{max}\) is calculated using
any pair of pressure rise and airflow values that correspond
with maximum fan static efficiency for the specified fan. Must
be greater than zero.
Field:
Maximum Dimensionless Fan Airflow[LINK]
The required numeric maximum dimensionless airflow (\(\psi_{max}\)) through the fan,
which corresponds to the maximum ratio between the airflow
through the fan (\(Q_{fan}\),
m\(^{3}\)/sec) and the fan
shaft rotational speed (\(\omega_{fan}\), rpm) for
the specified fan wheel diameter (D\(_{fan}\), m). \(\varphi_{max}\) is determined
from manufacturers data using:
\[\varphi_{\max} = \frac{30}{\pi
D_{fan}^3} \cdot \max \left( \frac{Q_{fan}}{\omega_{fan}}
\right)\]
\(\varphi_{max}\) occurs
at minimum Eu, which corresponds to maximum speed
(high flow) with zero pressure rise. The factor (\(30/\pi\)) converts revolutions
per minute (rpm) to rad/s. Must be greater than zero.
Field: Motor Fan Pulley
Ratio[LINK]
The numeric dimensionless ratio of the motor pulley
diameter to the fan pulley diameter (D\(_{motor,pulley}\) / D\(_{fan,pulley}\)). If
specified, must be greater than zero. This ratio can be
adjusted to account for belt slip if the fractional slip is
known (multiply the drive ratio with no slip by 1+s, where s
is the belt fractional slip). Default is 1.0 if field is blank
(leave blank if no belt; i.e., direct drive). Can be autosized
(assumes no slip).
Specified or autosized motor/fan pulley diameter ratio is
reported in the .eio file as Drive Ratio [-]. Autosized ratio
is based on fan speed in revolutions per minute (rpm),
calculated at design flow condition, divided by Field: Motor
Maximum Speed.
Field: Belt Maximum
Torque[LINK]
The required numeric maximum output torque capacity of the
fan drive belt (\(\tau_{belt,max}\) [N-m]). If
specified, must be greater than zero. Can be autosized. Use
autosize if no belt (i.e., direct drive).
Specified or autosized belt maximum output torque
(including effects of scaling by Field: Belt Sizing Factor) is
reported in the .eio file as Design Belt Output Torque [N -m].
Also, calculated maximum belt efficiency corresponding to
Design Fan Shaft Power, along with belt efficiency at design
flow condition (including part-load effects of oversized
belt), are reported in the .eio file as, respectively, Maximum
Belt Efficiency [-] and Design Belt Efficiency [-].
Field: Belt Sizing
Factor[LINK]
The numeric dimensionless factor (F\(_{belt}\)) used to multiply
the specified or autosized fan shaft maximum output torque
(\(_{belt,max}\)*). If
specified, minimum value is 1.0. Default is 1.0 if field is
blank.
Field: Belt
Fractional Torque Transition[LINK]
The numeric transition point (x\(_{belt,trans}\)) between
performance curves for Regions 1 and 2 for the drive belt
normalized part-load efficiency. Must be between 0.0 and 1.0.
Default is 0.167 (corresponds to generic V-belt) if field is
blank.
Field: Motor Maximum
Speed[LINK]
The required numeric maximum rotational speed of the fan
motor shaft (\(\omega_{motor,max}\)) in
revolutions per minute (rpm). Typical values for motors
supplied by 60 Hz power are near 900, 1200, 1800, and 3600
rpm. Must be greater than zero.
Field: Maximum Motor
Output Power[LINK]
The required numeric maximum output power (input power to
the fan drive belt) by the motor (H\(_{belt,max}\), W). If
specified, must be greater than zero. Can be autosized. In the
case of direct drive, H\(_{belt,max}\) corresponds to
the maximum fan shaft power (H\(_{fan,max}\)).
Specified or autosized maximum motor output power
(including effects of scaling by Field: Motor Sizing Factor)
is reported in the .eio file as Design Motor Output Power [W].
Also, calculated maximum motor efficiency corresponding to
Design Motor Output Power, along with motor efficiency at
design flow condition (including part-load effects of
oversized motor), are reported in the .eio file as,
respectively, Maximum Motor Efficiency [-] and Design Motor
Efficiency [-]. Note that maximum motor efficiency often
occurs at less than full load.
Field: Motor Sizing
Factor[LINK]
The numeric dimensionless sizing factor (F\(_{motor}\)) used to multiply
the specified or autosized fan motor output power (H\(_{belt,max}\)). If
specified, minimum value is 1.0. Default is 1.0.
Field: Motor In
Airstream Fraction[LINK]
The numeric fraction of the combined motor and belt heat
that is added to the air stream. A value of 0.0 means that the
motor and belt are completely outside the air stream. A value
of 1.0 means that all of the motor and belt heat loss will go
into the air stream and act to cause an air enthalpy rise.
Must be between 0.0 and 1.0. Default is 1.0.
Field: VFD Efficiency
Type[LINK]
The alpha basis for calculating fan
variable-frequency-drive (VFD) efficiency: Power , which
corresponds to a function of the fraction of full-load motor
input power (H\(_{motor}\) / H\(_{motor,max}\)), or Speed ,
which corresponds to a function of the fraction of full-load
speed (\(\omega_{motor} /
\omega_{max}\)). If this field is blank, then it is
assumed that the VFD efficiency is 0.97. If no VFD is used,
then specify Power and also specify a VFD efficiency curve
with a constant value of 1.0 (see VFD Efficiency Curve Name
field for details).
Field: Maximum VFD
Output Power[LINK]
The required numeric maximum output power (input power to
the fan motor) by the variable frequency drive (H\(_{motor,max}\), W). If
specified, must be greater than zero. Can be autosized.
Specified or autosized maximum VFD output power (including
effects of scaling by Field: VFD Sizing Factor) and
corresponding VFD input power are reported in the .eio file
as, respectively, Design VFD Output Power [W] and Rated Power
[W]. Also, calculated VFD efficiency corresponding to Design
VFD Output Power (including part-load effects of oversized
VFD) along with corresponding combined system efficiency (fan,
belt, motor, and VFD efficiencies multiplied together) at
design flow condition are reported in the .eio file as,
respectively, Design VFD Efficiency [-] and Design Combined
Efficiency [-].
Field: VFD Sizing Factor[LINK]
The numeric dimensionless factor (F\(_{VFD}\)) used to multiply
the specified or autosized motor maximum input power
(H\(_{motor,max}\)).
If specified, minimum value is 1.0. Default is 1.0 if field is
blank.
Field: Fan
Pressure Rise Curve Name[LINK]
The required alpha name of the fan total pressure rise
performance curve (ref: Curve:FanPressureRise
in Performance Curves) that parameterizes the variation of fan
total pressure rise (P\(_{fan,tot}\), Pa) as a
function of volumetric flow through the fan (Q\(_{fan}\), m\(^{3}\)/s) and duct static
pressure set point (P\(_{sm}\), Pa). The fan outlet
velocity pressure is subtracted from the output of this curve
to determine fan static pressure rise, which is then used to
calculate a dimensionless Euler number at each time step. The
Euler number is in turn used to determine fan efficiency,
speed, and torque (the Euler number is defined in the
Euler Number at Maximum Fan Static Efficiency field).
This curve should be valid for the range of volumetric flows,
distribution system leakage, duct static pressures, and static
pressures surrounding the ducts anticipated for the simulation
period.
Field:
Duct Static Pressure Reset Curve Name[LINK]
The required alpha name of the performance curve that
parameterizes the variation of the duct static pressure set
point (\(P_{sm}\), Pa) as a
function of volumetric flow through the fan (\(Q_{fan}\), m\(^{3}\)/s), which is used so that
the resistance associated with VAV box damper operation is
reduced.
The output of this curve is used to calculate the duct
static pressure set point at each time step. This curve should
be valid for the range of duct static pressure set points and
volumetric flows, anticipated for the simulation period.
For an ad hoc linear duct static pressure reset scheme, the
relation (ref: Curve:Linear
in Performance Curves) between duct static pressure (\(P_{sm}\), Pa) and flow through
the fan (\(Q_{fan}\), m\(^{3}\)/s) for \(Q_{fan,min} \le Q_{fan} \le
Q_{fan,max}\) is:
\[P_{sm} = P_{sm,\min } + \left(
P_{sm,\max } - P_{sm,\min } \right) * \frac{{\left( {{Q_{fan}}
- {Q_{fan,\min }}} \right)}}{{\left( {{Q_{fan,\max }} -
{Q_{fan,\min }}} \right)}} = {C_1} +
{C_2}*{Q_{fan}}\]
where \({C_1} = {P_{sm,\min }} -
{C_2}*{Q_{fan,\min }}\) and \({C_2} = \frac{{\left( {{P_{sm,\max }} -
{P_{sm,\min }}} \right)}}{{\left( {{Q_{fan,\max }} -
{Q_{fan,\min }}} \right)}}\)
For Q\(_{fan}\)
< Q\(_{fan,min}\), P\(_{sm}\) = P\(_{sm,min}\);for Q\(_{fan}\) > Q\(_{fan,max}\), P\(_{sm}\) = P\(_{sm,max}\)
The minimum and maximum fan airflows (Q\(_{fan,min}\) and Q\(_{fan,max}\)) correspond
respectively to the minimum and maximum duct static pressure
set points (P\(_{sm,min}\) and P\(_{sm,max}\)).
If no duct static pressure reset scheme is used and the
duct static pressure set point is constant, then parameter
C\(_{2}\) is set to
zero and C\(_{1}\)
represents the constant duct static pressure set point.
Field:
Normalized Fan Static Efficiency Curve Name Non-Stall
Region[LINK]
The required alpha name of the exponential-modified skew
normal performance curve (ref: Curve:ExponentialSkewNormal
in Performance Curves) that parameterizes the normalized fan
static efficiency (\(\eta_{\rm{fan}}(x_{\rm{fan}}) /
\eta_{\rm{fan, max}}\)) at each time step for the
normal operating (non-stall) region of the fan performance map
as a function of \(x_{\rm{fan}}\), which is defined
as log-base-10 of Eu at the fan flow and pressure rise
operating point divided by Eu at maximum fan static efficiency
\([log_{10}(Eu /
Eu_{\rm{max}})]\). In this region, \(x_{\rm{fan}} \le 0\).
The output of this curve is used to calculate the fan
efficiency \(\eta_{\rm{fan}}
(x_{\rm{fan}})\) at each time step by modifying \(\eta_{\rm{fan, max}}\) (see
Maximum Fan Static Efficiency field). This curve
should have a maximum of 1.0 and should be valid for the range
of volumetric flows and fan pressure rises anticipated for the
simulation period.
Field:
Normalized Fan Static Efficiency Curve Name Stall Region[LINK]
The required alpha name of the exponential-modified skew
normal performance curve (ref: Curve:ExponentialSkewNormal
in Performance Curves) that parameterizes the normalized fan
static efficiency (\(\eta_{\rm{fan}}
(x_{\rm{fan}}) / \eta_{\rm{fan, max}}\)) at each time
step for the stall region of the fan performance map as a
function of \(x_{\rm{fan}}\)
(see Normalized Fan Static Efficiency Curve Name Non-Stall
Region field). In this region, \(x_{\rm{fan}} > 0\).
The output of this curve is used to calculate the fan
efficiency \(\eta_{\rm{fan}} (
x_{\rm{fan}} )\) at each time step by modifying \(\eta_{\rm{fan, max}}\) (see
Maximum Fan Static Efficiency field). This curve
should have a maximum of 1.0 and should be valid for the range
of volumetric flows and fan pressure rises anticipated for the
simulation period.
Field:
Normalized Dimensionless Airflow Curve Name Non-Stall
Region[LINK]
The required alpha name of the sigmoid performance curve
(ref: Curve:Sigmoid
in Performance Curves) that parameterizes the normalized
dimensionless airflow through the fan (\(\varphi (x_{\rm{fan}}) /
\varphi_{\rm{max}}\)) at each time step for the normal
operating (non-stall) region of the fan performance map as a
function of \(x_{\rm{fan}}\),
which is defined as log-base-10 of Eu at the fan flow and
pressure rise operating point divided by Eu at maximum fan
static efficiency \([log_{10}(Eu /
Eu_{\rm{max}})]\). In this region, \(x_{\rm{fan}} \le 0\).
The output of this curve is used to calculate the
dimensionless airflow \(\varphi
(x_{\rm{fan}})\) at each time step by modifying \(\varphi_{\rm{max}}\) (see
Maximum Dimensionless Fan Airflow field). This curve
should have a maximum of 1.0 and should be valid for the range
of volumetric flows and fan pressure rises anticipated for the
simulation period.
Field:
Normalized Dimensionless Airflow Curve Name Stall Region[LINK]
The required alpha name of the sigmoid performance curve
(ref: Curve:Sigmoid
in Performance Curves) that parameterizes the normalized
dimensionless airflow through the fan (\(\varphi (x_{\rm{fan}}) /
\varphi_{\rm{max}}\)) at each time step for the stall
region of the fan performance map as a function of \(x_{\rm{fan}}\) (see
Normalized Dimensionless Airflow Curve Name Non-Stall
Region field). In this region, \(x_{\rm{fan}} > 0\).
The output of this curve is used to calculate the
dimensionless airflow \(\varphi
(x_{\rm{fan}})\) at each time step by modifying \(\varphi_{\rm{max}}\) (see
Maximum Dimensionless Fan Airflow field). This curve
should have a maximum of 1.0 and should be valid for the range
of volumetric flows and fan pressure rises anticipated for the
simulation period.
Field:
Maximum Belt Efficiency Curve Name[LINK]
The alpha name of the quartic polynomial performance curve
(ref: Curve:Quartic
in Performance Curves) that determines the maximum fan drive
belt efficiency in logarithmic space (\(\eta_{\rm{belt, max, ln}}\)) as a
function of \(x_{\rm{belt,
max}}\). The curve is:
\[\eta_{\rm{belt, max, ln}} =
C_1 + C_2 \cdot x_{\rm{belt, max}} + C_3 \cdot x_{\rm{belt,
max}}^2 + C_4 \cdot x_{\rm{belt, max}}^3 + C_5 \cdot
x_{\rm{belt, max}}^4\]
where \(x_{\rm{belt, max}} =
ln(F_{\rm{belt}} \cdot H_{\rm{fan, max}})\) with \(H_{\rm{fan, max}}\) expressed in
terms of hp.
Note that \(\eta_{\rm{belt, max}}
= exp(\eta_{\rm{belt, max, ln}})\).
The output of this curve must be greater than zero and less
than or equal to 1.0. If \(\eta_{\rm{belt, max}}\) is known,
it is represented by coefficient \(C_1\) (\(= ln(\eta_{\rm{belt, max}})\)).
In this case, coefficients \(C_2\) through \(C_5\) are set to zero. If this
field is left blank (e.g., there is no belt), the model
assumes that the output of the modifier curve is 1.0 for the
entire simulation (maximum belt efficiency = 1.0).
Field:
Normalized Belt Efficiency Curve Name Region 1[LINK]
The alpha name of the single rectangular hyperbola type 2
performance curve (ref: Curve:RectangularHyperbola2
in Performance Curves) that determines the normalized
(par-load) fan drive belt efficiency (\(\eta_{\rm{belt}}(x_{\rm{belt}}) /
\eta_{\rm{belt, max}}\)) as a function of \(x_{\rm{belt}}\). Normalized belt
efficiency is represented by a segmented curve with three
different regions. The curve for Region 1 (\(0 \le x_{\rm{belt}} < x_{\rm{belt,
trans}}\)) is:
\[\frac{\eta_{\rm{belt}} (
x_{\rm{belt}} )}{\eta_{\rm{belt, max}}} = \frac{(C_1 \cdot
x_{\rm{belt}})}{(C_2 + x_{\rm{belt}})} + C_3 \cdot
x_{\rm{belt}}\]
where \(x_{\rm{belt}}\) =
\(\tau_{\rm{belt}} / \tau_{\rm{belt,
max}}\); \(\tau_{\rm{belt}}\) is the belt
output torque that corresponds to the calculated power input
to the fan shaft (\(H_{\rm{fan}}\), W) by the drive
belt and the calculated fan shaft speed (\(\omega_{\rm{fan}}\), rpm).
The output of this curve is used to calculate the belt
efficiency \(\eta_{\rm{belt}}
(x_{\rm{belt}})\) in Region 1 at each time step by
modifying \(\eta_{\rm{belt,
max}}\) (see Maximum Belt Efficiency Curve
Name field). The output of this curve must be greater
than zero and less than or equal to 1.0 and should be valid
for the range of volumetric flows and fan pressure rises
anticipated for the simulation period.
If this field is left blank, the model assumes that the
output of the modifier curve is 1.0 for the entire simulation
(i.e., constant belt efficiency at \(\eta_{\rm{belt, max}}\) in Region
1).
Field:
Normalized Belt Efficiency Curve Name Region 2[LINK]
The alpha name of the exponential decay performance curve
(ref: Curve:ExponentialDecay
in Performance Curves) that determines the normalized
(part-load) fan drive belt efficiency (\(\eta_{\rm{belt}} (x_{\rm{belt}}) /
\eta_{\rm{belt, max}}\)) as a function of \(x_{\rm{belt}}\). Normalized belt
efficiency is represented by a segmented curve with three
different regions. The curve for Region 2 (\(x_{\rm{belt, trans}} \le x_{\rm{belt}}
\le 1\)) is:
\[\eta_{\rm{belt}}
(x_{\rm{belt}}) / \eta_{\rm{belt, max}} = C_1 + C_2 \cdot
exp(C_3 \cdot x_{\rm{belt}})\]
where \(x_{\rm{belt}} =
\tau_{\rm{belt}} / \tau_{\rm{belt, max}}\); \(\tau_{\rm{belt}}\) is the belt
output torque that corresponds to the calculated power input
to the fan shaft (\(H_{\rm{fan}}\), W) by the drive
belt and the calculated fan shaft speed (\(\omega_{\rm{fan}}\), rpm).
The output of this curve is used to calculate the belt
efficiency \(\eta_{\rm{belt}}
(x_{\rm{belt}}\) in Region 2 at each time step by
modifying \(\eta_{\rm{belt,
max}}\) (see Maximum Belt Efficiency Curve
Name field). The output of this curve must be greater
than zero and less than or equal to 1.0 and should be valid
for the range of volumetric flows and fan pressure rises
anticipated for the simulation period.
If this field is left blank, the model assumes that the
output of the modifier curve is 1.0 for the entire simulation
(i.e., constant belt efficiency at \(\eta_{\rm{belt, max}}\) in Region
2).
Field:
Normalized Belt Efficiency Curve Name Region 3[LINK]
The alpha name of the single rectangular hyperbola type 2
performance curve (ref: Curve:RectangularHyperbola2
in Performance Curves) that determines the normalized
(part-load) fan drive belt efficiency (\(\eta_{\rm{belt}} (x_{\rm{belt}}) /
\eta_{\rm{belt, max}}\)) as a function of \(x_{\rm{belt}}\). Normalized belt
efficiency is represented by a segmented curve with three
different regions. The curve for Region 3 (\(x_{\rm{belt}} > 1\)) is:
\[\eta_{\rm{belt}} (
x_{\rm{belt}} ) / \eta_{\rm{belt, max}} = ( C_1 \cdot
x_{\rm{belt}} ) / ( C_2 + x_{\rm{belt}} ) + C_3 \cdot
x_{\rm{belt}}\]
where \(x_{\rm{belt}} =
\tau_{\rm{belt}} / \tau_{\rm{belt, max}}\); \(\tau_{\rm{belt}}\) is the belt
output torque that corresponds to the calculated power input
to the fan shaft (\(H_{\rm{fan}}\), W) by the drive
belt and the calculated fan shaft speed (\(\omega_{\rm{fan}}\), rpm).
The output of this curve is used to calculate the belt
efficiency \(\eta_{\rm{belt}}
(x_{\rm{belt}})\) in Region 3 at each time step by
modifying \(\eta_{\rm{belt,
max}}\) (see Maximum Belt Efficiency Curve
Name field). The output of this curve must be greater
than zero and less than or equal to 1.0 and should be valid
for the range of volumetric flows and fan pressure rises
anticipated for the simulation period.
If this field is left blank, the model assumes that the
output of the modifier curve is 1.0 for the entire simulation
(i.e., constant belt efficiency at \(\eta_{\rm{belt, max}}\) in Region
3).
Field:
Maximum Motor Efficiency Curve Name[LINK]
The alpha name of the single rectangular hyperbola type 1
performance curve (ref: Curve: RectangularHyperbola1 in
Performance Curves) that determines the maximum fan motor
efficiency (\(\eta_{\rm{motor,
max}}\)) as a function of \(x_{\rm{motor, max}}\). The curve
is:
\[\eta_{\rm{motor, max}} = (C_1
\cdot x_{\rm{motor, max}}) / (C_2 + x_{\rm{motor, max}}) +
C_3\]
where \(x_{\rm{motor, max}} =
ln(F_{\rm{motor}} \cdot H_{\rm{belt, max}})\) with
\(H_{\rm{belt, max}}\)
expressed in terms of hp. \(H_{\rm{belt, max}}\) is the
maximum output power from the motor to the belt, which
corresponds to the calculated maximum power input to the fan
shaft (\(H_{\rm{fan, max}}\),
W).
The output of this curve must be greater than zero and less
than or equal to 1.0. If \(\eta_{\rm{motor, max}}\) is
known, it is represented by coefficient \(C_3\). In this case, coefficients
\(C_1\) and \(C_2\) are set to zero.
If this field is left blank, the model assumes that the
output of the modifier curve is 1.0 for the entire simulation
(maximum motor efficiency = 1.0).
Field:
Normalized Motor Efficiency Curve Name[LINK]
The name of the HVAC system node to which the fan sends its
outlet air.
The alpha name of the single rectangular hyperbola type 2
performance curve (ref: Curve:RectangularHyperbola2
in Performance Curves) that determines the normalized
(part-load) fan motor efficiency (\(\eta_{\rm{motor}} (x_{\rm{motor}})
/ \eta_{\rm{motor, max}}\)) as a function of the motor
load fraction \(x_{\rm{motor}}\). The curve
is:
\[\eta_{\rm{motor}}
(x_{\rm{motor}}) / \eta_{\rm{motor, max}} = (C_1 \cdot
x_{\rm{motor}}) / (C_2 + x_{\rm{motor}}) + (C_3 \cdot
x_{\rm{motor}}\]
where \(x_{\rm{motor}} =
H_{\rm{belt}} / H_{\rm{belt, max}}\). \(H_{\rm{belt}}\) is the calculated
output power from the motor to the belt (W), which corresponds
to the calculated power input to the fan shaft (\(H_{\rm{fan}}\), W).
The output of this curve is used to calculate the motor
efficiency (\(\eta_{\rm{motor}}
(x_{\rm{motor}})\)) at each time step by modifying
\(\eta_{\rm{motor, max}}\)
(see Maximum Motor Efficiency Curve Name field). The
output of this curve must be greater than zero and less than
or equal to 1.0 and should be valid for the range of
volumetric flows and fan pressure rises anticipated for the
simulation period.
If this field is left blank, the model assumes that the
output of the modifier curve is 1.0 for the entire simulation
(i.e., constant motor efficiency at \(\eta_{\rm{motor, max}}\)).
Field: VFD Efficiency
Curve Name[LINK]
The alpha name of the single rectangular hyperbola type 2
performance curve (e.g., Curve:RectangularHyperbola2
in Performance Curves) that determines the VFD efficiency
(\(\eta_{VFD}(x_{VFD})\)) as
a function of the fractional input power of the motor or
fractional motor speed (\(x_{VFD}\)). An example of the
curve is:
\[\eta_{VFD}(x_{VFD}) = (C_1
\cdot x_{VFD}) / (C_2 + x_{VFD}) + C_3 \cdot
x_{VFD}\]
where \(x_{VFD} = H_{\rm{motor}}
/ H_{\rm{motor, max}}\) or \(\omega_{\rm{motor}} / \omega_{\rm{motor,
max}}\).
The output of this curve is used to calculate the VFD
efficiency \(\eta_{VFD}(x_{VFD})\) at each
time step. The output of this curve must be greater than zero
and less than or equal to 1.0 and should be valid for the
range of volumetric flows and fan pressure rises anticipated
for the simulation period.
If this field is left blank, the model assumes that the
output of the modifier curve is 0.97 for the entire simulation
(i.e., constant VFD efficiency of 0.97).
Field: End-Use
Subcategory[LINK]
Allows you to specify a user-defined end-use subcategory,
e.g., “Central System”. A new meter for reporting is created
for each unique subcategory (ref: Output:Meter
objects). Subcategories are also reported in the ABUPS table.
If this field is omitted or blank, the fan will be assigned to
the “General” end-use subcategory.
An example of use in an IDF:
Fan:ComponentModel,
Supply Fan 1, ! Fan Name
Main Heating Coil 1 Outlet Node, ! Inlet Node Name
VAV Sys 1 Outlet Node, ! Outlet Node Name
FanAvailSched, ! Fan Schedule
autosize, ! Maximum Flow Rate [m3/s]
autosize, ! Minimum Flow Rate [m3/s]
1.0, ! Fan Sizing Factor [-]
0.3048, ! Fan Wheel Diameter [m]
0.0873288576, ! Fan Outlet Area [m2]
0.514, ! Maximum Fan Static Efficiency [-]
9.76, ! Euler Number at Maximum Fan Static Efficiency [-]
0.160331811647483, ! Maximum Dimensionless Fan Airflow [-]
autosize, ! Motor/Fan Pulley Ratio [-]
autosize, ! Belt Maximum Torque [N m]
1.0, ! Belt Sizing Factor [-]
0.167, ! Belt Fractional Torque Transition [-]
1800, ! Motor Maximum Speed [rpm]
autosize, ! Maximum Motor Output Power [W]
1.0, ! Motor Sizing Factor [-]
1.0, ! Motor In Airstream Fraction [-]
Power, ! VFD Efficiency Type
autosize, ! Maximum VFD Output Power [W]
1.0, ! VFD Sizing Factor [-]
VSD Example, ! Fan Pressure Rise Curve Name
DiagnosticSPR, ! Duct Static Pressure Reset Curve Name
FanEff120CPLANormal, ! Fan Efficiency Curve Name Non-Stall
FanEff120CPLAStall, ! Fan Efficiency Curve Name - Stall
FanDimFlowNormal, ! Dimensionless Airflow Curve Name-Non-Stall
FanDimFlowStall, ! Dimensionless Airflow Curve Name-Stall
BeltMaxEffMedium, ! Maximum Belt Efficiency Curve Name
BeltPartLoadRegion1, ! Normalized Belt Efficiency Curve Name
BeltPartLoadRegion2, ! Normalized Belt Efficiency Curve Name
BeltPartLoadRegion3, ! Normalized Belt Efficiency Curve Name
MotorMaxEffAvg, ! Maximum Motor Efficiency Curve Name
MotorPartLoad, ! Normalized Motor Efficiency Curve Name
VFDPartLoad; ! VFD Efficiency Curve Name
HVAC,Average,Fan Electric Power[W]
HVAC,Average,Fan Rise in Air Temperature
[deltaC]
HVAC,Sum,Fan Electric Energy [J]
Fan Electric Power [W][LINK]
This output field contains the average electricity
consumption rate for the fan in Watts for the timestep being
reported.
Fan Rise in Air
Temperature [deltaC][LINK]
This output field contains the average rise in air
temperature across the fan (outlet air temperature minus inlet
air temperature) in degrees Celsius for the timestep being
reported.
Fan Electric Energy [J][LINK]
This output field contains the electricity consumption of
the fan in Joules for the timestep being reported. This output
is also added to a meter with Resource Type = Electricity, End
Use Key = Fans, Group Key = System (ref. Output:Meter
objects).
Other Outputs[LINK]
Several parameters input by the user or calculated during
component sizing for the design condition (maximum system
airflow) are reported separately in the <filename>.eio
file. These parameters include fan airflow and pressure rise;
fan shaft input, motor output, VFD output, and VFD input
(rated) power; pulley drive ratio; belt output torque; and
fan, belt, motor, VFD, and combined system efficiencies. They
can be identified by lines in the .eio file beginning with
Component Sizing Information, Fan:ComponentModel
. The same values are also reported under the
ComponentSizingSummary heading in the
<filename>Table.html file.
Group Fans[LINK]
The following fans may be defined either in the air loop or as a zone equipment component: Fan:ConstantVolume, Fan:OnOff, Fan:VariableVolume, Fan:ZoneExhaust, and FanPerformance:NightVentilation. The data that are common to these fan types include an identifying name, an availability schedule name, a total efficiency rating, a rated pressure rise, and inlet and outlet air node names. In the case of a variable volume fan, additional input includes parameters for modeling fan performance over a range of fan speeds. See the engineering documentation for the variable speed fan for a further description of what these coefficients represent. Commonly-used values for different variable volume systems are shown in the following table.
Fan:ConstantVolume[LINK]
This object models a constant air volume fan that is intended to operate continuously based on a time schedule. This fan will not cycle on and off based on cooling/heating load or other control signals (Ref: Fan:OnOff).
Inputs[LINK]
Field: Name[LINK]
A unique user-assigned name for an instance of a Fan:ConstantVolume. Any reference to this fan by another object will use this name.
Field: Availability Schedule Name[LINK]
The name of the schedule (ref: Schedule) that denotes whether the fan can run during a given time period. A schedule value of 0 indicates that the fan is off for that time period. A schedule value greater than 0 indicates that the fan can operate during the time period. If this field is blank, the schedule has values of 1 for all time periods. Applicable availability managers (ref. AvailabilityManagerAssignmentList) may override this schedule by forcing the fan to be on or off.
Field: Fan Total Efficiency[LINK]
This value is the overall efficiency of the fan, i.e., the ratio of the power delivered to the fluid to the electrical input power. It is the product of the motor efficiency and the impeller efficiency. The motor efficiency is the power delivered to the shaft divided by the electrical power input to the motor. The impeller efficiency is power delivered to the fluid (air) divided by the shaft power. The power delivered to the fluid is the mass flow rate of the air multiplied by the pressure rise divided by the air density. This input value must be between 0 and 1.The default is 0.7.
Field: Pressure Rise[LINK]
The pressure rise in Pascals at full flow and standard (sea level) conditions (20 °C and 101325 Pa).
Field: Maximum Flow Rate[LINK]
The full load air volumetric flow rate (m\(^{3}\)/sec) at standard temperature and pressure (dry air at 20 °C drybulb). The program does use local barometric pressure to account for altitude using equation for “standard atmospheric” pressure on p 6.1 of the ASHRAE 1997 HOF (SI edition) to initialize the air systems being simulated.
p = 101325*(1-2.25577E-05*Z)**5.2559
where p = pressure in Pa and Z = altitude in m
Field: Motor Efficiency[LINK]
The shaft power divided by the electrical power consumed. Must be between 0 and 1. The default is 0.9.
Field: Motor In Airstream Fraction[LINK]
The fraction of the motor heat that is added to the air stream. A value of 0 means that the motor is completely outside the air stream. A value of 1 means that all of the motor heat loss will go into the air stream and act to cause a temperature rise. Must be between 0 and 1. The default is 1.0.
Field: Air Inlet Node Name[LINK]
The name of the HVAC system node which supplies the inlet air conditions to the fan.
Field: Air Outlet Node Name[LINK]
The name of the HVAC system node to which the fan sends its outlet air.
Field: End-Use Subcategory[LINK]
Allows you to specify a user-defined end-use subcategory, e.g., “Central System”, etc. A new meter for reporting is created for each unique subcategory (ref: Output:Meter objects). Subcategories are also reported in the ABUPS table. If this field is omitted or blank, the fan will be assigned to the “General” end-use subcategory.
Outputs[LINK]
HVAC,Average,Fan Electric Power[W]
HVAC,Average,Fan Rise in Air Temperature [deltaC]
HVAC,Sum,Fan Electric Energy [J]
Fan Electric Power [W][LINK]
This output field contains the average electricity consumption rate for the fan in Watts for the timestep being reported.
Fan Rise in Air Temperature [deltaC][LINK]
This output field contains the average rise in air temperature across the fan (outlet air temperature minus inlet air temperature) in degrees Celsius for the timestep being reported.
Fan Electric Energy [J][LINK]
This output field contains the electricity consumption of the fan in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Fans, Group Key = System (ref. Output:Meter objects).
Fan:OnOff[LINK]
This object models a constant air volume fan that is intended to cycle on and off in tandem with a cooling or heating system (i.e., AUTO fan control mode). The fan can also operate continuously like Fan:ConstantVolume. If modeling continuous operation and this object is used as part of a system that utilizes Coil:Heating:Gas, Coil:Cooling:DX:SingleSpeed or Coil:Heating:DX:SingleSpeed, the user should confirm proper air flow rates (coil and fan max flows are equal) and that the coil part-load fraction correlation(s) are appropriate (e.g., part-load fraction is less than or equal to 1 for all values of coil part-load ratio). If modeling multi-speed fan operation, this object must be used as part of a compound object that allows multiple fan speeds (e.g., AirLoopHVAC:Unitary:Furnace:HeatCool, ZoneHVAC:PackagedTerminalAirConditioner, etc.). In this case, the ratio of the compound object air flow rate to the fan s maximum air flow rate is used to determine the power at alternate fan speeds. The optional input for Fan Power Ratio Function of Speed Ratio Curve Name must be entered to model multi-speed fan operation. An optional fan total efficiency ratio curve is also available to model efficiency differences at alternate fan speeds.
Inputs[LINK]
Field: Name[LINK]
A unique user-assigned name for an instance of a Fan:OnOff. Any reference to this fan by another object will use this name.
Field: Availability Schedule Name[LINK]
The name of the schedule (ref: Schedule) that denotes whether the fan can run during a given time period. A schedule value of 0 indicates that the fan is off for that time period. A schedule value greater than 0 indicates that the fan can operate during the time period. If this field is blank, the schedule has values of 1 for all time periods. Applicable availability managers (ref. AvailabilityManagerAssignmentList) may override this schedule by forcing the fan to be on or off.
Field: Fan Total Efficiency[LINK]
This value is the overall efficiency of the fan, i.e., the ratio of the power delivered to the fluid to the electrical input power. It is the product of the motor efficiency and the impeller efficiency. The motor efficiency is the power delivered to the shaft divided by the electrical power input to the motor. The impeller efficiency is power delivered to the fluid (air) divided by the shaft power. The power delivered to the fluid is the mass flow rate of the air multiplied by the pressure rise divided by the air density. This input value must be between 0 and 1.The default is 0.6.
Field: Pressure Rise[LINK]
The pressure rise in Pascals at full flow and standard (sea level) conditions (20 °C and 101325 Pa).
Field: Maximum Flow Rate[LINK]
The full load air volumetric flow rate (m\(^{3}\)/sec) at standard temperature and pressure (dry air at 20 °C drybulb). The program does use local barometric pressure to account for altitude using equation for “standard atmospheric” pressure on p 6.1 of the ASHRAE 1997 HOF (SI edition) to initialize the air systems being simulated.
p = 101325*(1-2.25577E-05*Z)**5.2559
where p = pressure in Pa and Z = altitude in m
Field: Motor Efficiency[LINK]
The shaft power divided by the electrical power consumed. Must be between 0 and 1. The default is 0.8.
Field: Motor In Airstream Fraction[LINK]
The fraction of the motor heat that is added to the air stream. A value of 0 means that the motor is completely outside the air stream. A value of 1 means that all of the motor heat loss will go into the air stream and act to cause a temperature rise. Must be between 0 and 1. The default is 1.0.
Field: Air Inlet Node Name[LINK]
The name of the HVAC system node which supplies the inlet air conditions to the fan.
Field: Air Outlet Node Name[LINK]
The name of the HVAC system node to which the fan sends its outlet air.
Field: Fan Power Ratio Function of Speed Ratio Curve Name[LINK]
Enter the name of an exponent performance curve. This optional alpha field must be used to simulate multi-speed fan motors. This curve represents the ratio of actual fan power to rated fan power when a change in fan speed occurs. Leave this field blank when simulating constant-speed fan motors.
Field: Fan Efficiency Ratio Function of Speed Ratio Curve Name[LINK]
Enter the name of a quadratic or cubic performance curve. This optional alpha field is used to simulate multi-speed fan motors. This curve represents the ratio of actual fan total efficiency to rated fan total efficiency when a change in fan speed occurs. Leave this field blank when simulating constant-speed fan motors.
Field: End-Use Subcategory[LINK]
Allows you to specify a user-defined end-use subcategory, e.g., “Main Fans”, etc. A new meter for reporting is created for each unique subcategory (ref: Output:Meter objects). Subcategories are also reported in the ABUPS table. If this field is omitted or blank, the fan will be assigned to the “General” end-use subcategory.
Following is an example input for an OnOff Fan.
Outputs[LINK]
HVAC,Average,Fan Electric Power[W]
HVAC,Average,Fan Rise in Air Temperature [deltaC]
HVAC,Sum,Fan Electric Energy [J]
HVAC,Average,Fan Runtime Fraction []
Fan Electric Power [W][LINK]
This output field contains the average electricity consumption rate for the fan in Watts for the timestep being reported.
Fan Rise in Air Temperature [deltaC][LINK]
This output field contains the average rise in air temperature across the fan (outlet air temperature minus inlet air temperature) in degrees Celsius for the timestep being reported.
Fan Electric Energy [J][LINK]
This output field contains the electricity consumption of the fan in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Fans, Group Key = System (ref. Output:Meter objects).
Fan Runtime Fraction [][LINK]
This output field contains the fraction of time that this fan operated for the timestep being reported.
Fan:VariableVolume[LINK]
Inputs[LINK]
Field: Name[LINK]
A unique user-assigned name for an instance of a Fan:VariableVolume. Any reference to this fan by another object will use this name.
Field: Availability Schedule Name[LINK]
The name of the schedule (ref: Schedule) that denotes whether the fan can run during a given time period. A schedule value of 0 indicates that the fan is off for that time period. A schedule value greater than 0 indicates that the fan can operate during the time period. If this field is blank, the schedule has values of 1 for all time periods. Applicable availability managers (ref. AvailabilityManagerAssignmentList) may override this schedule by forcing the fan to be on or off.
Field: Fan Total Efficiency[LINK]
This value is the overall efficiency of the fan, i.e., the ratio of the power delivered to the fluid to the electrical input power. It is the product of the motor efficiency and the impeller efficiency. The motor efficiency is the power delivered to the shaft divided by the electrical power input to the motor. The impeller efficiency is power delivered to the fluid (air) divided by the shaft power. The power delivered to the fluid is the mass flow rate of the air multiplied by the pressure rise divided by the air density. This input value must be between 0 and 1. The default is 0.7.
Field: Pressure Rise[LINK]
The pressure rise in Pascals at full flow and standard (sea level) conditions (20 °C and 101325 Pa).
Field: Maximum Flow Rate[LINK]
The full load air volumetric flow rate (m\(^{3}\)/sec) at standard temperature and pressure (dry air at 20 °C drybulb). The program does use local barometric pressure to account for altitude using equation for “standard atmospheric” pressure on p 6.1 of the ASHRAE 1997 HOF (SI edition) to initialize the air systems being simulated.
p = 101325*(1-2.25577E-05*Z)**5.2559
where p = pressure in Pa and Z = altitude in m
Field: Fan Power Minimum Flow Rate Input Method[LINK]
This field is a key/choice field that tells which of the next two fields is filled and is descriptive of how the minimum flow rate is specified for calculating the fan power. The key/choices are:
With this choice, the fan power will be calculated using the value specified in the Fan Power Minimum Flow Fraction field. (The Fan Power Minimum Flow Fraction field should be filled.)
With this choice, the fan power will be calculated using the value specified in the Fan Power Minimum Air Flow Rate field. (The Fan Power Minimum Air Flow Rate field should be filled.)
The default is Fraction.
Field: Fan Power Minimum Flow Fraction[LINK]
The minimum air volumetric flow rate for fan power, specified as a fraction of maximum system air flow rate. Must be between 0 and 1. Note that this field is only used to calculate the fan power. This field does not enforce the system air flow rate during simulation. The default is 0.25.
Field: Fan Power Minimum Air Flow Rate[LINK]
The minimum air volumetric flow rate for fan power, specified as a constant minimum air flow rate (m3/sec). Note that this field is only used to calculate the fan power. This field does not enforce the system air flow rate during simulation.
Field: Motor Efficiency[LINK]
The shaft power divided by the electrical power consumed. Must be between 0 and 1. The default is 0.9.
Field: Motor In Airstream Fraction[LINK]
The fraction of the motor heat that is added to the air stream. A value of 0 means that the motor is completely outside the air stream. A value of 1 means that all of the motor heat loss will go into the air stream and act to cause a temperature rise. Must be between 0 and 1. The default is 1.0.
Field: Fan Power Coefficient 1[LINK]
The constant coefficient (C\(_{1}\)) in a fourth order polynomial curve giving the fraction of full load power (PLF) as a function of flow fraction (FF). Flow fraction is the air mass flow rate divided by the maximum air mass flow rate. The curve is:
PLF = C\(_{1}\) + C\(_{2}\)\(^{.}\) FF + C\(_{3}\)\(^{.}\) FF\(^{2\\ +}\) C\(_{4}\)\(^{.}\) FF\(^{3}\) + C\(_{5}\)\(^{.}\) FF\(^{4}\)
Field: Fan Power Coefficient 2[LINK]
The linear coefficient (C\(_{2}\)) in a fourth order polynomial curve giving the fraction of full load power (PLF) as a function of flow fraction (FF). Flow fraction is the air mass flow rate divided by the maximum air mass flow rate. The curve is:
PLF = C\(_{1}\) + C\(_{2}\)\(^{.}\) FF + C\(_{3}\)\(^{.}\) FF\(^{2\\ +}\) C\(_{4}\)\(^{.}\) FF\(^{3}\) + C\(_{5}\)\(^{.}\) FF\(^{4}\)
Field: Fan Power Coefficient 3[LINK]
The quadratic coefficient (C\(_{3}\)) in a fourth order polynomial curve giving the fraction of full load power (PLF) as a function of flow fraction (FF). Flow fraction is the air mass flow rate divided by the maximum air mass flow rate. The curve is:
PLF = C\(_{1}\) + C\(_{2}\)\(^{.}\) FF + C\(_{3}\)\(^{.}\) FF\(^{2\\ +}\) C\(_{4}\)\(^{.}\) FF\(^{3}\) + C\(_{5}\)\(^{.}\) FF\(^{4}\)
Field: Fan Power Coefficient 4[LINK]
The cubic coefficient (C\(_{1}\)) in a fourth order polynomial curve giving the fraction of full load power (PLF) as a function of flow fraction (FF). Flow fraction is the air mass flow rate divided by the maximum air mass flow rate. The curve is:
Field: Fan Power Coefficient 5[LINK]
The coefficient C\(_{5}\) in a fourth order polynomial curve giving the fraction of full load power (PLF) as a function of flow fraction (FF). Flow fraction is the air mass flow rate divided by the maximum air mass flow rate. The curve is:
Field: Air Inlet Node Name[LINK]
The name of the HVAC system node which supplies the inlet air conditions to the fan.
Field: Air Outlet Node Name[LINK]
The name of the HVAC system node to which the fan sends its outlet air.
Field: End-Use Subcategory[LINK]
Allows you to specify a user-defined end-use subcategory, e.g., “Central System”, etc. A new meter for reporting is created for each unique subcategory (ref: Output:Meter objects). Subcategories are also reported in the ABUPS table. If this field is omitted or blank, the fan will be assigned to the “General” end-use subcategory.
Outputs[LINK]
HVAC,Average,Fan Electric Power[W]
HVAC,Average,Fan Rise in Air Temperature [deltaC]
HVAC,Sum,Fan Electric Energy [J]
Fan Electric Power [W][LINK]
This output field contains the average electricity consumption rate for the fan in Watts for the timestep being reported.
Fan Rise in Air Temperature [deltaC][LINK]
This output field contains the average rise in air temperature across the fan (outlet air temperature minus inlet air temperature) in degrees Celsius for the timestep being reported.
Fan Electric Energy [J][LINK]
This output field contains the electricity consumption of the fan in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Fans, Group Key = System (ref. Output:Meter objects).
Fan:ZoneExhaust[LINK]
This fan object differs from the other fans in that it stands on its own in a zone rather than serving as one part of an HVAC air system. This object appears directly in a ZoneHVAC:EquipmentList object and all the controls are contained within the fan object. The zone exhaust fan model provides a way to include the electrical power used by the fan. It can also impact air flows in central air handlers by decreasing the flow of return air and sometimes increasing the outdoor air flow rate.
There are several control options available for the exhaust fan including: an on/off availability schedule, interaction with system availability managers, minimum zone air temperature control limits and a variable flow fraction schedule.
The way in which the exhaust fan impacts central air system can be controlled by declaring what portion of the flow has been balanced by simple airflow from infiltration, ventilation, or mixing. However it is important to note that presence of an exhaust fan does not by itself drive any simple airflow such as infiltration, ventilation, or zone mixing. There is no comprehensive automatic mass balancing between air system flows, exhaust flows, and the separate simple airflows. For balancing, the simple airflows need to have their own input objects that need to be coordinated with the exhaust fan.
Inputs[LINK]
Field: Name[LINK]
A unique user-assigned name for an instance of a Fan:ZoneExhaust. Any reference to this fan by another object will use this name.
Field: Availability Schedule Name[LINK]
The name of the schedule (ref: Schedule) that denotes whether the fan can run during a given time period. A schedule value of 0 indicates that the fan is off for that time period. A schedule value greater than 0 indicates that the fan can operate during the time period. If this field is blank, the schedule has values of 1 for all time periods. Applicable availability managers (ref. AvailabilityManagerAssignmentList) may override this schedule by forcing the fan to be on or off.
Field: Fan Total Efficiency[LINK]
This value is the overall efficiency of the fan, i.e., the ratio of the power delivered to the fluid to the electrical input power. It is the product of the motor efficiency and the impeller efficiency. The motor efficiency is the power delivered to the shaft divided by the electrical power input to the motor. The impeller efficiency is power delivered to the fluid (air) divided by the shaft power. The power delivered to the fluid is the mass flow rate of the air multiplied by the pressure rise divided by the air density. This input value must be between 0 and 1. The default is 0.6.
Field: Pressure Rise[LINK]
The pressure rise in Pascals at full flow and standard (sea level) conditions (20 °C and 101325 Pa).
Field: Maximum Flow Rate[LINK]
The full load air volumetric flow rate (m\(^{3}\)/sec) at standard temperature and pressure (dry air at 20 °C drybulb). The program does use local barometric pressure to account for altitude using equation for “standard atmospheric” pressure on p 6.1 of the ASHRAE 1997 HOF (SI edition) to initialize the air systems being simulated.
p = 101325*(1-2.25577E-05*Z)**5.2559
where p = pressure in Pa and Z = altitude in m
Field: Air Inlet Node Name[LINK]
The name of the HVAC system node which supplies the inlet air conditions to the fan. This node should be listed as a zone exhaust node in an associated ZoneHVAC:EquipmentConnections object.
Field: Air Outlet Node Name[LINK]
The name of the HVAC system node to which the fan sends its outlet air.
Field: End-Use Subcategory[LINK]
Allows you to specify a user-defined end-use subcategory, e.g., “Kitchen Exhaust”, “Fume Hoods”, etc. A new meter for reporting is created for each unique subcategory (ref: Output:Meter objects). Subcategories are also reported in the ABUPS table. If this field is omitted or blank, the fan will be assigned to the “General” end-use subcategory.
Field: Flow Fraction Schedule Name[LINK]
This field is optional. If it is not used then the fan operates at the maximum flow rate. If a schedule is input here, then it should contain fractional values between 0.0 and 1.0, inclusive. The flow rate that the fan operates will be this fraction times the maximum flow rate. This allows a variable speed exhaust fan to be modeled according to a schedule.
Field: System Availability Manager Coupling Mode[LINK]
This field is optional. If if is not used then the exhaust fan is assumed to be integrated with the central air handler s system availability manager. This field can be used to control if the exhaust fan should operate independently or not. For example, when a night cycle availability manager turns on the central air system for freeze protection, this field can be used to control if the zone exhaust fans should also run at the same time or not. The key choice Coupled indicates that the exhaust fan should be integrated with the system availability manager so that the fan runs when the air system is forced to run. The key choice Decoupled indicates that the exhaust fan should operate on its own and ignore the system availability manager s requests so that the exhaust fan can remain off when the air system runs. The default is Coupled.
Field: Minimum Zone Temperature Limit Schedule Name[LINK]
This field is optional. If it is not used then there will be no temperature-related control over the operation of the exhaust fan. If the field is used, then enter the name of a schedule with values for zone temperature values ( °C). The fan s control will be based on a comparison between the current zone air temperature and the schedule values. If the zone is warmer than the scheduled limit, then the fan will operate. When balancing with simple ventilation, this feature can be used to coordinate exhaust fan operation with ZoneVentilation:* controls for minimum indoor temperature.
Field: Balanced Exhaust Fraction Schedule Name[LINK]
This field is optional. If it is not used, then all the exhaust air flow is assumed to be unbalanced by any simple airflows, such as infiltration, ventilation, or zone mixing. Unbalanced exhaust is then modeled as being provided by the outdoor air system in the central air system. The modeling of unbalanced will reduce the flow rates at the zone s return air node by the flow rate that is being exhausted and will insure that the outdoor air flow rate is sufficient to serve the exhaust. If this field is used, then enter the name of a schedule with fractional values between 0.0 and 1.0, inclusive. This fraction is applied to the exhaust fan flow rate and the model tracks the portion of the exhaust that is balanced. Balanced exhaust is then modeled as being provided by simple airflows and does not impact the central air system return air or outdoor air flow rates. For example, if a kitchen zone with an exhaust fan is designed to draw half of its make up air from a neighboring dining room and the other half from the outdoor air system, then a schedule value of 0.5 could be used here.
Outputs[LINK]
HVAC,Average,Fan Electric Power [W]
HVAC,Average,Fan Rise in Air Temperature[deltaC]
HVAC,Sum,Fan Electric Energy [J]
HVAC,Average,Fan Unbalanced Air Mass Flow Rate [kg/s]
HVAC,Average,Fan Balanced Air Mass Flow Rate [kg/s]
Fan Electric Power [W][LINK]
This output field contains the average electricity consumption rate for the fan in Watts for the timestep being reported.
Fan Rise in Air Temperature [deltaC][LINK]
This output field contains the average rise in air temperature across the fan (outlet air temperature minus inlet air temperature) in degrees Celsius for the timestep being reported.
Fan Electric Energy [J][LINK]
This output field contains the electricity consumption of the fan in Joules for the timestep being reported. This output is also added to an output meter with Resource Type = Electricity, End Use Key = Fans, Group Key = System (ref. Output:Meter objects).
Fan Unbalanced Air Mass Flow Rate [kg/s][LINK]
Fan Balanced Air Mass Flow Rate [kg/s][LINK]
These two output variables are available when the exhaust fan uses the input field called Balanced Exhaust Fraction Schedule Name. The balanced air flow is the result of the current flow rate times the balance fraction. The unbalanced air flow is the difference between the current flow rate and the balanced flow rate. These outputs are the resulting flow rates in kg/s.
Examples of Fan:ConstantVolume, Fan:VariableVolume, Fan:ZoneExhaust, and , Fan:OnOff, fans in an IDF are:
FanPerformance:NightVentilation[LINK]
This object is used for specifying an alternate set of performance parameters for a fan. These alternate parameters are used when a system manager (such as AvailabilityManager:NightVentilation) sets a specified flow rate for a central forced air system. At this time, it can be used with Fan:ConstantVolume, Fan:VariableVolume, Fan:ZoneExhaust, and , Fan:OnOff fans, but not with Fan:ComponentModel fans. The fan model checks whether a fixed flow rate has been set; if it has the fan model will use these alternate performance parameters. Note that it is assumed that the fan will run at a fixed speed in the alternate mode. The inputs needed by this object are the fan name, fan total efficiency, pressure rise, flow rate, motor efficiency, and motor in airstream fraction.
Inputs[LINK]
Field: Fan Name[LINK]
This is the name of a fan defined elsewhere in the input file. The night vent performance parameters will be applied to the named fan when a system manager has set the air system flow rate.
Field: Fan Total Efficiency[LINK]
This value is the overall efficiency of the fan, i.e., the ratio of the power delivered to the fluid to the electrical input power. It is the product of the motor efficiency and the impeller efficiency. The motor efficiency is the power delivered to the shaft divided by the electrical power input to the motor. The impeller efficiency is power delivered to the fluid (air) divided by the shaft power. The power delivered to the fluid is the mass flow rate of the air multiplied by the pressure rise divided by the air density. This input value must be between 0 and 1. This is a required field with no default.
Field: Pressure Rise[LINK]
The pressure rise in Pascals at full flow and standard (sea level) conditions (20 °C and 101325 Pa).
Field: Maximum Flow Rate[LINK]
The design volumetric flow rate of the fan (m\(^{3}\)/sec) at standard conditions. This input is not currently used by the night ventilation manager. The flow rate during night ventilation is specified using the SystemAvailabilityManager:NightVentilation “Night Venting Flow Fraction” field. This fraction is multiplied times the fan object’s design flow rate.
Field: Motor Efficiency[LINK]
The shaft power divided by the electrical power consumed. Must be between 0 and 1. This is a required field with no default.
Field: Motor in Airstream Fraction[LINK]
The fraction of the motor heat that is added to the air stream. A value of 0 means that the motor is completely outside the air stream. A value of 1 means that all of the motor heat loss will go into the air stream and act to cause a temperature rise. Must be between 0 and 1. The default is 1.0.
An example of use in an IDF:
Fan:ComponentModel[LINK]
The Fan:ComponentModel fan is a more detailed fan type that can be defined in the air loop for central constant-air-volume (CAV) and variable-air-volume (VAV) systems. It includes inputs that describe the air-distribution system as well as the fan, its drive belt (if used), its motor, and its variable-frequency-drive (if used). See the engineering documentation for further descriptions about the inputs for this fan type.
Inputs[LINK]
Field: Name[LINK]
The required unique user-assigned alpha name for an instance of a Fan:ComponentModel. Any reference to this fan by another object will use this name.
Field: Air Inlet Node Name[LINK]
The required alpha name of the HVAC system node which supplies the inlet air conditions to the fan.
Field: Air Outlet Node Name[LINK]
The required alpha name of the HVAC system node to which the fan sends its outlet air.
Field: Availability Schedule Name[LINK]
The required alpha name of the schedule (ref: Schedule) that denotes whether the fan can run during a given time period. A schedule value of 0 indicates that the fan is off for that time period. A schedule value greater than 0 indicates that the fan can operate during the time period. If this field is blank, the schedule has values of 1 for all time periods. Applicable availability managers (ref. AvailabilityManagerAssignmentList) may override this schedule by forcing the fan to be on or off.
Field: Maximum Flow Rate[LINK]
The full-load volumetric airflow (m\(^{3}\)/sec) through the fan at standard temperature and pressure (dry air at 20 °C dry-bulb). To initialize the air systems being simulated, the program uses local barometric pressure adjusted for altitude, based on the equation for “standard atmospheric” pressure on p.6.1 of the 1997 ASHRAE Handbook of Fundamentals (SI edition):
p = 101325 * (1 - 2.25577E-05 * Z)**5.2559
where p = pressure in Pa and Z = altitude in m. Can be autosized.
Specified or autosized maximum airflow rate (including effects of scaling by Field: Fan Sizing Factor) along with corresponding fan static pressure rise and fan shaft power are reported in the .eio file as, respectively, Design Fan Airflow [m3/s], Design Fan Static Pressure Rise [Pa], and Design Fan Shaft Power [W].
Field: Minimum Flow Rate[LINK]
The minimum volumetric airflow (m\(^{3}\)/sec) through the fan at standard temperature and pressure (see Maximum Flow Rate field above for condition details). Can be autosized.
Field: Fan Sizing Factor[LINK]
The numeric dimensionless factor (F\(_{fan}\)) used to multiply the specified or autosized full-load volumetric airflow (see Maximum Flow Rate field above for details) for fan sizing. If specified, minimum value is 1.0. Default is 1.0 if field is blank.
Field: Fan Wheel Diameter[LINK]
The required numeric outer diameter of the fan wheel (D\(_{fan}\), m). This value is determined from manufacturer s data. In general, larger diameter fans have higher maximum efficiency than smaller diameter fans of the same type (Ref: AMCA Standard 205-10: Energy Efficiency Classification for Fans). Must be greater than zero.
Field: Fan Outlet Area[LINK]
The required numeric outlet area of the fan (A\(_{fan,out}\), m\(^{2}\)). This value is determined from manufacturer s data. It is used to convert fan total pressure rise to fan static pressure rise. Fan static pressure rise is the fan total pressure rise minus the fan outlet velocity pressure; it is not the difference between fan outlet and inlet static pressures (Ref: ANSI/AMCA Standard 210-07, ANSI/ASHRAE Standard 51-07: Laboratory Methods of Testing Fans for Certified Aerodynamic Performance Rating). Must be greater than zero.
Field: Maximum Fan Static Efficiency[LINK]
The required numeric maximum ratio (\(\eta_{fan,max}\) ) between the power delivered to the air (H\(_{air}\), W) and the fan shaft input power (H\(_{fan}\), W). For this parameter, H\(_{air}\) is the volumetric airflow through the fan multiplied by the fan static pressure rise. Maximum fan static efficiency is determined from analyses of manufacturers data using:
\[{\eta_{fan,\max }} = \max \left[ {\frac{{\left( {\Delta {P_{fan}} * {Q_{fan}}} \right)}}{{{H_{fan}}}}} \right]\]
where P\(_{fan}\) is fan static pressure rise (Pa) and Q\(_{fan}\) is airflow through the fan (m\(^{3}\)/sec). Typically, do not select curves on fan performance maps of pressure rise versus flow correspond to or are near maximum efficiency. Must be greater than zero and less than or equal to 1.0.
Calculated fan static efficiency at design flow condition (including part-load effects of oversized fan) is reported in the .eio file as Design Fan Efficiency [-].
Field: Euler Number at Maximum Fan Static Efficiency[LINK]
The required numeric Euler number (Eu\(_{max}\)), which is also called the throttling or pressure coefficient, and is the ratio of pressure forces to inertial forces. The Euler number is determined from analyses of manufacturer s data using:
\[Eu = \frac{{\left( {\Delta {P_{fan}} * D_{fan}^4} \right)}}{{\left( {\rho * Q_{fan}^2} \right)}}\]
where P\(_{fan}\) is fan static pressure rise (Pa; see Fan Pressure Rise Curve Name field), D\(_{fan}\) is wheel diameter (m), ρ is the manufacturer s reference air density (kg/m\(^{3}\)), and Q\(_{fan}\) is airflow through the fan (m\(^{3}\)/sec). Eu\(_{max}\) is calculated using any pair of pressure rise and airflow values that correspond with maximum fan static efficiency for the specified fan. Must be greater than zero.
Field: Maximum Dimensionless Fan Airflow[LINK]
The required numeric maximum dimensionless airflow (\(\psi_{max}\)) through the fan, which corresponds to the maximum ratio between the airflow through the fan (\(Q_{fan}\), m\(^{3}\)/sec) and the fan shaft rotational speed (\(\omega_{fan}\), rpm) for the specified fan wheel diameter (D\(_{fan}\), m). \(\varphi_{max}\) is determined from manufacturers data using:
\[\varphi_{\max} = \frac{30}{\pi D_{fan}^3} \cdot \max \left( \frac{Q_{fan}}{\omega_{fan}} \right)\]
\(\varphi_{max}\) occurs at minimum Eu, which corresponds to maximum speed (high flow) with zero pressure rise. The factor (\(30/\pi\)) converts revolutions per minute (rpm) to rad/s. Must be greater than zero.
Field: Motor Fan Pulley Ratio[LINK]
The numeric dimensionless ratio of the motor pulley diameter to the fan pulley diameter (D\(_{motor,pulley}\) / D\(_{fan,pulley}\)). If specified, must be greater than zero. This ratio can be adjusted to account for belt slip if the fractional slip is known (multiply the drive ratio with no slip by 1+s, where s is the belt fractional slip). Default is 1.0 if field is blank (leave blank if no belt; i.e., direct drive). Can be autosized (assumes no slip).
Specified or autosized motor/fan pulley diameter ratio is reported in the .eio file as Drive Ratio [-]. Autosized ratio is based on fan speed in revolutions per minute (rpm), calculated at design flow condition, divided by Field: Motor Maximum Speed.
Field: Belt Maximum Torque[LINK]
The required numeric maximum output torque capacity of the fan drive belt (\(\tau_{belt,max}\) [N-m]). If specified, must be greater than zero. Can be autosized. Use autosize if no belt (i.e., direct drive).
Specified or autosized belt maximum output torque (including effects of scaling by Field: Belt Sizing Factor) is reported in the .eio file as Design Belt Output Torque [N -m]. Also, calculated maximum belt efficiency corresponding to Design Fan Shaft Power, along with belt efficiency at design flow condition (including part-load effects of oversized belt), are reported in the .eio file as, respectively, Maximum Belt Efficiency [-] and Design Belt Efficiency [-].
Field: Belt Sizing Factor[LINK]
The numeric dimensionless factor (F\(_{belt}\)) used to multiply the specified or autosized fan shaft maximum output torque (\(_{belt,max}\)*). If specified, minimum value is 1.0. Default is 1.0 if field is blank.
Field: Belt Fractional Torque Transition[LINK]
The numeric transition point (x\(_{belt,trans}\)) between performance curves for Regions 1 and 2 for the drive belt normalized part-load efficiency. Must be between 0.0 and 1.0. Default is 0.167 (corresponds to generic V-belt) if field is blank.
Field: Motor Maximum Speed[LINK]
The required numeric maximum rotational speed of the fan motor shaft (\(\omega_{motor,max}\)) in revolutions per minute (rpm). Typical values for motors supplied by 60 Hz power are near 900, 1200, 1800, and 3600 rpm. Must be greater than zero.
Field: Maximum Motor Output Power[LINK]
The required numeric maximum output power (input power to the fan drive belt) by the motor (H\(_{belt,max}\), W). If specified, must be greater than zero. Can be autosized. In the case of direct drive, H\(_{belt,max}\) corresponds to the maximum fan shaft power (H\(_{fan,max}\)).
Specified or autosized maximum motor output power (including effects of scaling by Field: Motor Sizing Factor) is reported in the .eio file as Design Motor Output Power [W]. Also, calculated maximum motor efficiency corresponding to Design Motor Output Power, along with motor efficiency at design flow condition (including part-load effects of oversized motor), are reported in the .eio file as, respectively, Maximum Motor Efficiency [-] and Design Motor Efficiency [-]. Note that maximum motor efficiency often occurs at less than full load.
Field: Motor Sizing Factor[LINK]
The numeric dimensionless sizing factor (F\(_{motor}\)) used to multiply the specified or autosized fan motor output power (H\(_{belt,max}\)). If specified, minimum value is 1.0. Default is 1.0.
Field: Motor In Airstream Fraction[LINK]
The numeric fraction of the combined motor and belt heat that is added to the air stream. A value of 0.0 means that the motor and belt are completely outside the air stream. A value of 1.0 means that all of the motor and belt heat loss will go into the air stream and act to cause an air enthalpy rise. Must be between 0.0 and 1.0. Default is 1.0.
Field: VFD Efficiency Type[LINK]
The alpha basis for calculating fan variable-frequency-drive (VFD) efficiency: Power , which corresponds to a function of the fraction of full-load motor input power (H\(_{motor}\) / H\(_{motor,max}\)), or Speed , which corresponds to a function of the fraction of full-load speed (\(\omega_{motor} / \omega_{max}\)). If this field is blank, then it is assumed that the VFD efficiency is 0.97. If no VFD is used, then specify Power and also specify a VFD efficiency curve with a constant value of 1.0 (see VFD Efficiency Curve Name field for details).
Field: Maximum VFD Output Power[LINK]
The required numeric maximum output power (input power to the fan motor) by the variable frequency drive (H\(_{motor,max}\), W). If specified, must be greater than zero. Can be autosized.
Specified or autosized maximum VFD output power (including effects of scaling by Field: VFD Sizing Factor) and corresponding VFD input power are reported in the .eio file as, respectively, Design VFD Output Power [W] and Rated Power [W]. Also, calculated VFD efficiency corresponding to Design VFD Output Power (including part-load effects of oversized VFD) along with corresponding combined system efficiency (fan, belt, motor, and VFD efficiencies multiplied together) at design flow condition are reported in the .eio file as, respectively, Design VFD Efficiency [-] and Design Combined Efficiency [-].
Field: VFD Sizing Factor[LINK]
The numeric dimensionless factor (F\(_{VFD}\)) used to multiply the specified or autosized motor maximum input power (H\(_{motor,max}\)). If specified, minimum value is 1.0. Default is 1.0 if field is blank.
Field: Fan Pressure Rise Curve Name[LINK]
The required alpha name of the fan total pressure rise performance curve (ref: Curve:FanPressureRise in Performance Curves) that parameterizes the variation of fan total pressure rise (P\(_{fan,tot}\), Pa) as a function of volumetric flow through the fan (Q\(_{fan}\), m\(^{3}\)/s) and duct static pressure set point (P\(_{sm}\), Pa). The fan outlet velocity pressure is subtracted from the output of this curve to determine fan static pressure rise, which is then used to calculate a dimensionless Euler number at each time step. The Euler number is in turn used to determine fan efficiency, speed, and torque (the Euler number is defined in the Euler Number at Maximum Fan Static Efficiency field). This curve should be valid for the range of volumetric flows, distribution system leakage, duct static pressures, and static pressures surrounding the ducts anticipated for the simulation period.
Field: Duct Static Pressure Reset Curve Name[LINK]
The required alpha name of the performance curve that parameterizes the variation of the duct static pressure set point (\(P_{sm}\), Pa) as a function of volumetric flow through the fan (\(Q_{fan}\), m\(^{3}\)/s), which is used so that the resistance associated with VAV box damper operation is reduced.
The output of this curve is used to calculate the duct static pressure set point at each time step. This curve should be valid for the range of duct static pressure set points and volumetric flows, anticipated for the simulation period.
For an ad hoc linear duct static pressure reset scheme, the relation (ref: Curve:Linear in Performance Curves) between duct static pressure (\(P_{sm}\), Pa) and flow through the fan (\(Q_{fan}\), m\(^{3}\)/s) for \(Q_{fan,min} \le Q_{fan} \le Q_{fan,max}\) is:
\[P_{sm} = P_{sm,\min } + \left( P_{sm,\max } - P_{sm,\min } \right) * \frac{{\left( {{Q_{fan}} - {Q_{fan,\min }}} \right)}}{{\left( {{Q_{fan,\max }} - {Q_{fan,\min }}} \right)}} = {C_1} + {C_2}*{Q_{fan}}\]
where \({C_1} = {P_{sm,\min }} - {C_2}*{Q_{fan,\min }}\) and \({C_2} = \frac{{\left( {{P_{sm,\max }} - {P_{sm,\min }}} \right)}}{{\left( {{Q_{fan,\max }} - {Q_{fan,\min }}} \right)}}\)
For Q\(_{fan}\) < Q\(_{fan,min}\), P\(_{sm}\) = P\(_{sm,min}\);for Q\(_{fan}\) > Q\(_{fan,max}\), P\(_{sm}\) = P\(_{sm,max}\)
The minimum and maximum fan airflows (Q\(_{fan,min}\) and Q\(_{fan,max}\)) correspond respectively to the minimum and maximum duct static pressure set points (P\(_{sm,min}\) and P\(_{sm,max}\)).
If no duct static pressure reset scheme is used and the duct static pressure set point is constant, then parameter C\(_{2}\) is set to zero and C\(_{1}\) represents the constant duct static pressure set point.
Field: Normalized Fan Static Efficiency Curve Name Non-Stall Region[LINK]
The required alpha name of the exponential-modified skew normal performance curve (ref: Curve:ExponentialSkewNormal in Performance Curves) that parameterizes the normalized fan static efficiency (\(\eta_{\rm{fan}}(x_{\rm{fan}}) / \eta_{\rm{fan, max}}\)) at each time step for the normal operating (non-stall) region of the fan performance map as a function of \(x_{\rm{fan}}\), which is defined as log-base-10 of Eu at the fan flow and pressure rise operating point divided by Eu at maximum fan static efficiency \([log_{10}(Eu / Eu_{\rm{max}})]\). In this region, \(x_{\rm{fan}} \le 0\).
The output of this curve is used to calculate the fan efficiency \(\eta_{\rm{fan}} (x_{\rm{fan}})\) at each time step by modifying \(\eta_{\rm{fan, max}}\) (see Maximum Fan Static Efficiency field). This curve should have a maximum of 1.0 and should be valid for the range of volumetric flows and fan pressure rises anticipated for the simulation period.
Field: Normalized Fan Static Efficiency Curve Name Stall Region[LINK]
The required alpha name of the exponential-modified skew normal performance curve (ref: Curve:ExponentialSkewNormal in Performance Curves) that parameterizes the normalized fan static efficiency (\(\eta_{\rm{fan}} (x_{\rm{fan}}) / \eta_{\rm{fan, max}}\)) at each time step for the stall region of the fan performance map as a function of \(x_{\rm{fan}}\) (see Normalized Fan Static Efficiency Curve Name Non-Stall Region field). In this region, \(x_{\rm{fan}} > 0\).
The output of this curve is used to calculate the fan efficiency \(\eta_{\rm{fan}} ( x_{\rm{fan}} )\) at each time step by modifying \(\eta_{\rm{fan, max}}\) (see Maximum Fan Static Efficiency field). This curve should have a maximum of 1.0 and should be valid for the range of volumetric flows and fan pressure rises anticipated for the simulation period.
Field: Normalized Dimensionless Airflow Curve Name Non-Stall Region[LINK]
The required alpha name of the sigmoid performance curve (ref: Curve:Sigmoid in Performance Curves) that parameterizes the normalized dimensionless airflow through the fan (\(\varphi (x_{\rm{fan}}) / \varphi_{\rm{max}}\)) at each time step for the normal operating (non-stall) region of the fan performance map as a function of \(x_{\rm{fan}}\), which is defined as log-base-10 of Eu at the fan flow and pressure rise operating point divided by Eu at maximum fan static efficiency \([log_{10}(Eu / Eu_{\rm{max}})]\). In this region, \(x_{\rm{fan}} \le 0\).
The output of this curve is used to calculate the dimensionless airflow \(\varphi (x_{\rm{fan}})\) at each time step by modifying \(\varphi_{\rm{max}}\) (see Maximum Dimensionless Fan Airflow field). This curve should have a maximum of 1.0 and should be valid for the range of volumetric flows and fan pressure rises anticipated for the simulation period.
Field: Normalized Dimensionless Airflow Curve Name Stall Region[LINK]
The required alpha name of the sigmoid performance curve (ref: Curve:Sigmoid in Performance Curves) that parameterizes the normalized dimensionless airflow through the fan (\(\varphi (x_{\rm{fan}}) / \varphi_{\rm{max}}\)) at each time step for the stall region of the fan performance map as a function of \(x_{\rm{fan}}\) (see Normalized Dimensionless Airflow Curve Name Non-Stall Region field). In this region, \(x_{\rm{fan}} > 0\).
The output of this curve is used to calculate the dimensionless airflow \(\varphi (x_{\rm{fan}})\) at each time step by modifying \(\varphi_{\rm{max}}\) (see Maximum Dimensionless Fan Airflow field). This curve should have a maximum of 1.0 and should be valid for the range of volumetric flows and fan pressure rises anticipated for the simulation period.
Field: Maximum Belt Efficiency Curve Name[LINK]
The alpha name of the quartic polynomial performance curve (ref: Curve:Quartic in Performance Curves) that determines the maximum fan drive belt efficiency in logarithmic space (\(\eta_{\rm{belt, max, ln}}\)) as a function of \(x_{\rm{belt, max}}\). The curve is:
\[\eta_{\rm{belt, max, ln}} = C_1 + C_2 \cdot x_{\rm{belt, max}} + C_3 \cdot x_{\rm{belt, max}}^2 + C_4 \cdot x_{\rm{belt, max}}^3 + C_5 \cdot x_{\rm{belt, max}}^4\]
where \(x_{\rm{belt, max}} = ln(F_{\rm{belt}} \cdot H_{\rm{fan, max}})\) with \(H_{\rm{fan, max}}\) expressed in terms of hp.
Note that \(\eta_{\rm{belt, max}} = exp(\eta_{\rm{belt, max, ln}})\).
The output of this curve must be greater than zero and less than or equal to 1.0. If \(\eta_{\rm{belt, max}}\) is known, it is represented by coefficient \(C_1\) (\(= ln(\eta_{\rm{belt, max}})\)). In this case, coefficients \(C_2\) through \(C_5\) are set to zero. If this field is left blank (e.g., there is no belt), the model assumes that the output of the modifier curve is 1.0 for the entire simulation (maximum belt efficiency = 1.0).
Field: Normalized Belt Efficiency Curve Name Region 1[LINK]
The alpha name of the single rectangular hyperbola type 2 performance curve (ref: Curve:RectangularHyperbola2 in Performance Curves) that determines the normalized (par-load) fan drive belt efficiency (\(\eta_{\rm{belt}}(x_{\rm{belt}}) / \eta_{\rm{belt, max}}\)) as a function of \(x_{\rm{belt}}\). Normalized belt efficiency is represented by a segmented curve with three different regions. The curve for Region 1 (\(0 \le x_{\rm{belt}} < x_{\rm{belt, trans}}\)) is:
\[\frac{\eta_{\rm{belt}} ( x_{\rm{belt}} )}{\eta_{\rm{belt, max}}} = \frac{(C_1 \cdot x_{\rm{belt}})}{(C_2 + x_{\rm{belt}})} + C_3 \cdot x_{\rm{belt}}\]
where \(x_{\rm{belt}}\) = \(\tau_{\rm{belt}} / \tau_{\rm{belt, max}}\); \(\tau_{\rm{belt}}\) is the belt output torque that corresponds to the calculated power input to the fan shaft (\(H_{\rm{fan}}\), W) by the drive belt and the calculated fan shaft speed (\(\omega_{\rm{fan}}\), rpm).
The output of this curve is used to calculate the belt efficiency \(\eta_{\rm{belt}} (x_{\rm{belt}})\) in Region 1 at each time step by modifying \(\eta_{\rm{belt, max}}\) (see Maximum Belt Efficiency Curve Name field). The output of this curve must be greater than zero and less than or equal to 1.0 and should be valid for the range of volumetric flows and fan pressure rises anticipated for the simulation period.
If this field is left blank, the model assumes that the output of the modifier curve is 1.0 for the entire simulation (i.e., constant belt efficiency at \(\eta_{\rm{belt, max}}\) in Region 1).
Field: Normalized Belt Efficiency Curve Name Region 2[LINK]
The alpha name of the exponential decay performance curve (ref: Curve:ExponentialDecay in Performance Curves) that determines the normalized (part-load) fan drive belt efficiency (\(\eta_{\rm{belt}} (x_{\rm{belt}}) / \eta_{\rm{belt, max}}\)) as a function of \(x_{\rm{belt}}\). Normalized belt efficiency is represented by a segmented curve with three different regions. The curve for Region 2 (\(x_{\rm{belt, trans}} \le x_{\rm{belt}} \le 1\)) is:
\[\eta_{\rm{belt}} (x_{\rm{belt}}) / \eta_{\rm{belt, max}} = C_1 + C_2 \cdot exp(C_3 \cdot x_{\rm{belt}})\]
where \(x_{\rm{belt}} = \tau_{\rm{belt}} / \tau_{\rm{belt, max}}\); \(\tau_{\rm{belt}}\) is the belt output torque that corresponds to the calculated power input to the fan shaft (\(H_{\rm{fan}}\), W) by the drive belt and the calculated fan shaft speed (\(\omega_{\rm{fan}}\), rpm).
The output of this curve is used to calculate the belt efficiency \(\eta_{\rm{belt}} (x_{\rm{belt}}\) in Region 2 at each time step by modifying \(\eta_{\rm{belt, max}}\) (see Maximum Belt Efficiency Curve Name field). The output of this curve must be greater than zero and less than or equal to 1.0 and should be valid for the range of volumetric flows and fan pressure rises anticipated for the simulation period.
If this field is left blank, the model assumes that the output of the modifier curve is 1.0 for the entire simulation (i.e., constant belt efficiency at \(\eta_{\rm{belt, max}}\) in Region 2).
Field: Normalized Belt Efficiency Curve Name Region 3[LINK]
The alpha name of the single rectangular hyperbola type 2 performance curve (ref: Curve:RectangularHyperbola2 in Performance Curves) that determines the normalized (part-load) fan drive belt efficiency (\(\eta_{\rm{belt}} (x_{\rm{belt}}) / \eta_{\rm{belt, max}}\)) as a function of \(x_{\rm{belt}}\). Normalized belt efficiency is represented by a segmented curve with three different regions. The curve for Region 3 (\(x_{\rm{belt}} > 1\)) is:
\[\eta_{\rm{belt}} ( x_{\rm{belt}} ) / \eta_{\rm{belt, max}} = ( C_1 \cdot x_{\rm{belt}} ) / ( C_2 + x_{\rm{belt}} ) + C_3 \cdot x_{\rm{belt}}\]
where \(x_{\rm{belt}} = \tau_{\rm{belt}} / \tau_{\rm{belt, max}}\); \(\tau_{\rm{belt}}\) is the belt output torque that corresponds to the calculated power input to the fan shaft (\(H_{\rm{fan}}\), W) by the drive belt and the calculated fan shaft speed (\(\omega_{\rm{fan}}\), rpm).
The output of this curve is used to calculate the belt efficiency \(\eta_{\rm{belt}} (x_{\rm{belt}})\) in Region 3 at each time step by modifying \(\eta_{\rm{belt, max}}\) (see Maximum Belt Efficiency Curve Name field). The output of this curve must be greater than zero and less than or equal to 1.0 and should be valid for the range of volumetric flows and fan pressure rises anticipated for the simulation period.
If this field is left blank, the model assumes that the output of the modifier curve is 1.0 for the entire simulation (i.e., constant belt efficiency at \(\eta_{\rm{belt, max}}\) in Region 3).
Field: Maximum Motor Efficiency Curve Name[LINK]
The alpha name of the single rectangular hyperbola type 1 performance curve (ref: Curve: RectangularHyperbola1 in Performance Curves) that determines the maximum fan motor efficiency (\(\eta_{\rm{motor, max}}\)) as a function of \(x_{\rm{motor, max}}\). The curve is:
\[\eta_{\rm{motor, max}} = (C_1 \cdot x_{\rm{motor, max}}) / (C_2 + x_{\rm{motor, max}}) + C_3\]
where \(x_{\rm{motor, max}} = ln(F_{\rm{motor}} \cdot H_{\rm{belt, max}})\) with \(H_{\rm{belt, max}}\) expressed in terms of hp. \(H_{\rm{belt, max}}\) is the maximum output power from the motor to the belt, which corresponds to the calculated maximum power input to the fan shaft (\(H_{\rm{fan, max}}\), W).
The output of this curve must be greater than zero and less than or equal to 1.0. If \(\eta_{\rm{motor, max}}\) is known, it is represented by coefficient \(C_3\). In this case, coefficients \(C_1\) and \(C_2\) are set to zero.
If this field is left blank, the model assumes that the output of the modifier curve is 1.0 for the entire simulation (maximum motor efficiency = 1.0).
Field: Normalized Motor Efficiency Curve Name[LINK]
The name of the HVAC system node to which the fan sends its outlet air.
The alpha name of the single rectangular hyperbola type 2 performance curve (ref: Curve:RectangularHyperbola2 in Performance Curves) that determines the normalized (part-load) fan motor efficiency (\(\eta_{\rm{motor}} (x_{\rm{motor}}) / \eta_{\rm{motor, max}}\)) as a function of the motor load fraction \(x_{\rm{motor}}\). The curve is:
\[\eta_{\rm{motor}} (x_{\rm{motor}}) / \eta_{\rm{motor, max}} = (C_1 \cdot x_{\rm{motor}}) / (C_2 + x_{\rm{motor}}) + (C_3 \cdot x_{\rm{motor}}\]
where \(x_{\rm{motor}} = H_{\rm{belt}} / H_{\rm{belt, max}}\). \(H_{\rm{belt}}\) is the calculated output power from the motor to the belt (W), which corresponds to the calculated power input to the fan shaft (\(H_{\rm{fan}}\), W).
The output of this curve is used to calculate the motor efficiency (\(\eta_{\rm{motor}} (x_{\rm{motor}})\)) at each time step by modifying \(\eta_{\rm{motor, max}}\) (see Maximum Motor Efficiency Curve Name field). The output of this curve must be greater than zero and less than or equal to 1.0 and should be valid for the range of volumetric flows and fan pressure rises anticipated for the simulation period.
If this field is left blank, the model assumes that the output of the modifier curve is 1.0 for the entire simulation (i.e., constant motor efficiency at \(\eta_{\rm{motor, max}}\)).
Field: VFD Efficiency Curve Name[LINK]
The alpha name of the single rectangular hyperbola type 2 performance curve (e.g., Curve:RectangularHyperbola2 in Performance Curves) that determines the VFD efficiency (\(\eta_{VFD}(x_{VFD})\)) as a function of the fractional input power of the motor or fractional motor speed (\(x_{VFD}\)). An example of the curve is:
\[\eta_{VFD}(x_{VFD}) = (C_1 \cdot x_{VFD}) / (C_2 + x_{VFD}) + C_3 \cdot x_{VFD}\]
where \(x_{VFD} = H_{\rm{motor}} / H_{\rm{motor, max}}\) or \(\omega_{\rm{motor}} / \omega_{\rm{motor, max}}\).
The output of this curve is used to calculate the VFD efficiency \(\eta_{VFD}(x_{VFD})\) at each time step. The output of this curve must be greater than zero and less than or equal to 1.0 and should be valid for the range of volumetric flows and fan pressure rises anticipated for the simulation period.
If this field is left blank, the model assumes that the output of the modifier curve is 0.97 for the entire simulation (i.e., constant VFD efficiency of 0.97).
Field: End-Use Subcategory[LINK]
Allows you to specify a user-defined end-use subcategory, e.g., “Central System”. A new meter for reporting is created for each unique subcategory (ref: Output:Meter objects). Subcategories are also reported in the ABUPS table. If this field is omitted or blank, the fan will be assigned to the “General” end-use subcategory.
An example of use in an IDF:
Outputs[LINK]
HVAC,Average,Fan Electric Power[W]
HVAC,Average,Fan Rise in Air Temperature [deltaC]
HVAC,Sum,Fan Electric Energy [J]
Fan Electric Power [W][LINK]
This output field contains the average electricity consumption rate for the fan in Watts for the timestep being reported.
Fan Rise in Air Temperature [deltaC][LINK]
This output field contains the average rise in air temperature across the fan (outlet air temperature minus inlet air temperature) in degrees Celsius for the timestep being reported.
Fan Electric Energy [J][LINK]
This output field contains the electricity consumption of the fan in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Fans, Group Key = System (ref. Output:Meter objects).
Other Outputs[LINK]
Several parameters input by the user or calculated during component sizing for the design condition (maximum system airflow) are reported separately in the <filename>.eio file. These parameters include fan airflow and pressure rise; fan shaft input, motor output, VFD output, and VFD input (rated) power; pulley drive ratio; belt output torque; and fan, belt, motor, VFD, and combined system efficiencies. They can be identified by lines in the .eio file beginning with Component Sizing Information, Fan:ComponentModel . The same values are also reported under the ComponentSizingSummary heading in the <filename>Table.html file.
Documentation content copyright © 1996-2026 The Board of Trustees of the University of Illinois and the Regents of the University of California through the Ernest Orlando Lawrence Berkeley National Laboratory. All rights reserved. EnergyPlus is a trademark of the US Department of Energy.
This documentation is made available under the EnergyPlus Open Source License v1.0.